tidy-up: whitespace, fix CI spacecheck for docs

Also: fixup CI spacecheck to apply to docs again.

Closes #15423

build: disable warning `-Wunreachable-code-break`

This warning remains silent in unity builds. Since we're using unity
in CI for most jobs, warnings remain undetected there.
Disable

build: disable warning `-Wunreachable-code-break`

This warning remains silent in unity builds. Since we're using unity
in CI for most jobs, warnings remain undetected there.
Disable them for all builds to avoid a surprise warning outside our CI.

The issue caught by the warning is useful for a tidy codebase, but
doesn't affect executed code. It was enabled in
84338c4de2d7c798e3c270c9610d51a4ad18a90b #12331 (2023-11-15).

llvm source: https://github.com/llvm/llvm-project/blob/fee2953f23bd8a8a71e574e6a8db08033778d3a4/clang/lib/Sema/AnalysisBasedWarnings.cpp#L125-L134
llvm issue: https://github.com/llvm/llvm-project/issues/71046

Follow-up to 7c023c3f6e2c454fbac7277d8dc038854c192d72 #15384
Closes #15416

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tidy-up: indentation in autotools sources

Indentation in `configure.ac` and `.m4` files.

Closes #14692

build: fix possible `-Wformat-overflow` in lib557 with test bundle builds

- lib557: suppress `-Wformat-overflow` warning in source.
Fixes:
```
lib557.c: In function ‘test_f

build: fix possible `-Wformat-overflow` in lib557 with test bundle builds

- lib557: suppress `-Wformat-overflow` warning in source.
Fixes:
```
lib557.c: In function ‘test_float_formatting’:
lib557.c:1408:37: error: ‘%*f’ directive output of 2147483648 bytes exceeds ‘INT_MAX’ [-Werror=format-overflow=]
1408 | curl_msnprintf(buf, sizeof(buf), "%*f", INT_MIN, 9.1);
| ^~~
lib557.c:1408:3: note: ‘curl_msnprintf’ output 2147483649 bytes
1408 | curl_msnprintf(buf, sizeof(buf), "%*f", INT_MIN, 9.1);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
Ref: https://app.circleci.com/pipelines/github/curl/curl/10226/workflows/87642ee9-cda6-4916-8206-c82aac5f595e/jobs/107669?invite=true#step-106-40996_46

The root cause of why this option gets enabled remains undiscovered.

Reported-by: Daniel Stenberg
Fixes #15008
Follow-up to 71cf0d1fca9e1f53524e1545ef0c08d174458d80 #14772

- build: drop `-Wno-format-overflow` from picky warning list.
These options only get used with picky warnings enabled.
Follow-up to 145f87b9e89f3a5e287233fe7d3cf57aca23dd8c #14598

- unit1652: suppress in source (and not rely on picky warnings anymore.)

Closes #15012

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tidy-up: indent, whitespace, `#error` in make files

Replace invalid C with `#error`.

Cherry-picked from #14692
Closes #14997

build: `buildinfo.txt` improvements

- cmake: drop `configure.os`.
This also includes OS version, but thus far it's not important enough
to include it.
- autotools: drop redun

build: `buildinfo.txt` improvements

- cmake: drop `configure.os`.
This also includes OS version, but thus far it's not important enough
to include it.
- autotools: drop redundant, autotools-only `{target|host}.vendor`.
(it's part of the triplet in `{target|host}`.)
- swap order to `*.cpu` -> `*.os` to match triplet-order.
- cmake: drop redundant `target`.
It's manually filled and only in a (so far) few CI jobs. Let's revisit
when this becomes useful.
- move `buildinfo.txt` to build root.
- dist: add `buildinfo.txt` to `DISTCLEANFILES`.
- autotools: detect human readable compiler version.
- autotools: replace `XXYY` `compiler.version` with "X.Y"-style.
(also to match cmake.)
- autotools: use distinct `compiler_id` for Apple clang: `APPLECLANG`.
To match cmake and also because the the "X.Y"-style version number
is the Apple version, while `XXYY` was a value roughly translated to
mainline llvm/clang version.
- show buildinfo at the end of the configure stage, when run in CI, or
when `CURL_BUILDINFO` or `CURL_CI` env is set.

Follow-up to 1fdea1684602a1ae2870c67b5f3e8fd34f63da95 #14802
Assisted-by: Dan Fandrich
Ref: https://github.com/curl/curl/pull/14802#issuecomment-2334942991
Closes #14822

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configure: fix indentation more

Follow-up to 0052b4b52dfbd6455a24dd95837e5236dc8e1f5d #14628

Closes #14682

configure: fix indentation

Also:
- move `then`s and an `in` inline.
- whitespace.

Closes #14628

build: improve compiler version detection portability

POSIX sed doesn't support extended regular expressions, so convert a
call to the basic format. This caused a problem on AIX. Also, u

build: improve compiler version detection portability

POSIX sed doesn't support extended regular expressions, so convert a
call to the basic format. This caused a problem on AIX. Also, use the
detected sed binary name instead of hard-coding one.

show more ...

build: use -Wno-format-overflow

-Wformat-overflow is not a warning that we want enabled as it does not
help us. It can only bring us false positives since it warns on bad uses
of spr

build: use -Wno-format-overflow

-Wformat-overflow is not a warning that we want enabled as it does not
help us. It can only bring us false positives since it warns on bad uses
of sprintf and vsprintf ("that might overflow the destination buffer").
Two functions we explicitly ban in curl code.

The only way this flag triggers warnings in curl code is false positives
for functions we have marked with the CURL_PRINTF() macro.

Further: it seems -Wformat-trunaction option might in turn also enable
-Wformat-overflow, so if this second option is used, we need to
explicitly set -Wno-format-overflow - not just skip setting
-Wformat-overflow.

Reported-by: Viktor Szakats
Fixes #14168
Closes #14598

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tidy-up: OS names

Use these words and casing more consistently across text, comments and
one curl tool output:
AIX, ALPN, ANSI, BSD, Cygwin, Darwin, FreeBSD, GitHub, HP-UX, Linux,

tidy-up: OS names

Use these words and casing more consistently across text, comments and
one curl tool output:
AIX, ALPN, ANSI, BSD, Cygwin, Darwin, FreeBSD, GitHub, HP-UX, Linux,
macOS, MS-DOS, MSYS, MinGW, NTLM, POSIX, Solaris, UNIX, Unix, Unicode,
WINE, WebDAV, Win32, winbind, WinIDN, Windows, Windows CE, Winsock.

Mostly OS names and a few more.

Also a couple of other minor text fixups.

Closes #14360

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build: sync warning options between autotools, cmake & compilers

- cmake: enable Apple-specific `-Werror=partial-availability` to match
autotools.

- autotools: enable `-pedant

build: sync warning options between autotools, cmake & compilers

- cmake: enable Apple-specific `-Werror=partial-availability` to match
autotools.

- autotools: enable `-pedantic-errors` with llvm/clang to match gcc and
CMake.

- autotools: enable `-Werror-implicit-function-declaration` for
llvm/clang to match gcc.

- cmake: enable `-Werror-implicit-function-declaration` to match
autotools.

- move `-Wpointer-bool-conversion` from autotools to the local file
(`sectransp.c`) it was meant to apply. This way it applies to all
build methods.

- autotoos: show `CURL_CFLAG_EXTRAS` in the `./configure` summary.
(it may contain `-Werror` and/or `-pedentic-errors`.)

Cherry-picked from #14097
Closes #14128

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build: add Debug, TrackMemory, ECH to feature list

Also:

- remove stray `ECH` and `HTTPSRR` from cmake protocol list.

- stop excluding `Debug` and `TrackMemory` in `test101

build: add Debug, TrackMemory, ECH to feature list

Also:

- remove stray `ECH` and `HTTPSRR` from cmake protocol list.

- stop excluding `Debug` and `TrackMemory` in `test1013.pl`.

- configure: delete `CURL_CHECK_CURLDEBUG` check.
Ref: 065047dc62cba3efde597fa5420d112fc2f4c500
This check was effectively doing nothing, except disabling
`--enable-curldebug` in `curl-config` for
Cygwin/MSYS/cegcc/OS2/AIX targets with c-ares enabled.

Closes #14096

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autotools: Only probe for SGI MIPS compilers on IRIX

MIPSPro and the predecessor compiler which was part of the IDO (IRIS
Development Option) were only ever shipped on the SGI IRIX opera

autotools: Only probe for SGI MIPS compilers on IRIX

MIPSPro and the predecessor compiler which was part of the IDO (IRIS
Development Option) were only ever shipped on the SGI IRIX operating
system (with MIPSPro on 6.0+ which was released in 1994). Limit the
autoconf check to IRIX when probing for these compilers to save some
cycles on other platforms.

Closes: #13611
Reviewed-by: Daniel Stenberg <daniel@haxx.se>

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build: fix some `-Wsign-conversion`/`-Warith-conversion` warnings

- enable `-Wsign-conversion` warnings, but also setting them to not
raise errors.
- fix `-Warith-conversion` warni

build: fix some `-Wsign-conversion`/`-Warith-conversion` warnings

- enable `-Wsign-conversion` warnings, but also setting them to not
raise errors.
- fix `-Warith-conversion` warnings seen in CI.
These are triggered by `-Wsign-converion` and causing errors unless
explicitly silenced. It makes more sense to fix them, there just a few
of them.
- fix some `-Wsign-conversion` warnings.
- hide `-Wsign-conversion` warnings with a `#pragma`.
- add macro `CURL_WARN_SIGN_CONVERSION` to unhide them on a per-build
basis.
- update a CI job to unhide them with the above macro:
https://github.com/curl/curl/actions/workflows/linux.yml -> OpenSSL -O3

Closes #12492

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windows: simplify detecting and using system headers

- autotools, cmake: assume that if we detect Windows, `windows.h`,
`winsock2.h` and `ws2tcpip.h` do exist.
- lib: fix 3 outlier

windows: simplify detecting and using system headers

- autotools, cmake: assume that if we detect Windows, `windows.h`,
`winsock2.h` and `ws2tcpip.h` do exist.
- lib: fix 3 outlier `#if` conditions to use `USE_WINSOCK` instead of
looking for `winsock2.h`.
- autotools: merge 3 Windows check methods into one.
- move Watt-32 and lwIP socket support to `setup-win32.h` from
`config-win32.h`. It opens up using these with all build tools. Also
merge logic with Windows Sockets.
- fix to assume Windows sockets with the mingw32ce toolchain.
Follow-up to: 2748c64d605b19fb419ae56810ad8da36487a2d4
- cmake: delete unused variable `signature_call_conv` since
eb33ccd5332435fa50f1758e5debb869c6942b7f.
- autotools: simplify `CURL_CHECK_WIN32_LARGEFILE` detection.
- examples/externalsocket: fix header order.
- cmake/OtherTests.cmake: delete Windows-specific `_source_epilogue`
that wasn't used anymore.
- cmake/OtherTests.cmake: set `WIN32_LEAN_AND_MEAN` for test
`SIZEOF_STRUCT_SOCKADDR_STORAGE`.

After this patch curl universally uses `_WIN32` to guard
Windows-specific logic. It guards Windows Sockets-specific logic with
`USE_WINSOCK` (this might need further work).

Reviewed-by: Jay Satiro
Closes #12495

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build: enable missing OpenSSF-recommended warnings, with fixes

https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.html
as of 2023-11-29 [1]

build: enable missing OpenSSF-recommended warnings, with fixes

https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.html
as of 2023-11-29 [1].

Enable new recommended warnings (except `-Wsign-conversion`):

- enable `-Wformat=2` for clang (in both cmake and autotools).
- add `CURL_PRINTF()` internal attribute and mark functions accepting
printf arguments with it. This is a copy of existing
`CURL_TEMP_PRINTF()` but using `__printf__` to make it compatible
with redefinting the `printf` symbol:
https://gcc.gnu.org/onlinedocs/gcc-3.0.4/gcc_5.html#SEC94
- fix `CURL_PRINTF()` and existing `CURL_TEMP_PRINTF()` for
mingw-w64 and enable it on this platform.
- enable `-Wimplicit-fallthrough`.
- enable `-Wtrampolines`.
- add `-Wsign-conversion` commented with a FIXME.
- cmake: enable `-pedantic-errors` the way we do it with autotools.
Follow-up to d5c0351055d5709da8f3e16c91348092fdb481aa #2747
- lib/curl_trc.h: use `CURL_FORMAT()`, this also fixes it to enable format
checks. Previously it was always disabled due to the internal `printf`
macro.

Fix them:

- fix bug where an `set_ipv6_v6only()` call was missed in builds with
`--disable-verbose` / `CURL_DISABLE_VERBOSE_STRINGS=ON`.
- add internal `FALLTHROUGH()` macro.
- replace obsolete fall-through comments with `FALLTHROUGH()`.
- fix fallthrough markups: Delete redundant ones (showing up as
warnings in most cases). Add missing ones. Fix indentation.
- silence `-Wformat-nonliteral` warnings with llvm/clang.
- fix one `-Wformat-nonliteral` warning.
- fix new `-Wformat` and `-Wformat-security` warnings.
- fix `CURL_FORMAT_SOCKET_T` value for mingw-w64. Also move its
definition to `lib/curl_setup.h` allowing use in `tests/server`.
- lib: fix two wrongly passed string arguments in log outputs.
Co-authored-by: Jay Satiro
- fix new `-Wformat` warnings on mingw-w64.

[1] https://github.com/ossf/wg-best-practices-os-developers/blob/56c0fde3895bfc55c8a973ef49a2572c507b2ae1/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C%2B%2B.md

Closes #12489

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build: add more picky warnings and fix them

Enable more picky compiler warnings. I've found these options in the
nghttp3 project when implementing the CMake quick picky warning
funct

build: add more picky warnings and fix them

Enable more picky compiler warnings. I've found these options in the
nghttp3 project when implementing the CMake quick picky warning
functionality for it [1].

`-Wunused-macros` was too noisy to keep around, but fixed a few issues
it revealed while testing.

- autotools: reflect the more precisely-versioned clang warnings.
Follow-up to 033f8e2a08eb1d3102f08c4d8c8e85470f8b460e #12324
- autotools: sync between clang and gcc the way we set `no-multichar`.
- autotools: avoid setting `-Wstrict-aliasing=3` twice.
- autotools: disable `-Wmissing-noreturn` for MSYS gcc targets [2].
It triggers in libtool-generated stub code.

- lib/timeval: delete a redundant `!MSDOS` guard from a `WIN32` branch.

- lib/curl_setup.h: delete duplicate declaration for `fileno`.
Added in initial commit ae1912cb0d494b48d514d937826c9fe83ec96c4d
(1999-12-29). This suggests this may not be needed anymore, but if
it does, we may restore this for those specific (non-Windows) systems.
- lib: delete unused macro `FTP_BUFFER_ALLOCSIZE` since
c1d6fe2aaa5a26e49a69a4f2495b3cc7a24d9394.
- lib: delete unused macro `isxdigit_ascii` since
f65f750742068f579f4ee6d8539ed9d5f0afcb85.
- lib/mqtt: delete unused macro `MQTT_HEADER_LEN`.
- lib/multi: delete unused macro `SH_READ`/`SH_WRITE`.
- lib/hostip: add `noreturn` function attribute via new `CURL_NORETURN`
macro.
- lib/mprintf: delete duplicate declaration for `Curl_dyn_vprintf`.
- lib/rand: fix `-Wunreachable-code` and related fallouts [3].
- lib/setopt: fix `-Wunreachable-code-break`.
- lib/system_win32 and lib/timeval: fix double declarations for
`Curl_freq` and `Curl_isVistaOrGreater` in CMake UNITY mode [4].
- lib/warnless: fix double declarations in CMake UNITY mode [5].
This was due to force-disabling the header guard of `warnless.h` to
to reapply it to source code coming after `warnless.c` in UNITY
builds. This reapplied declarations too, causing the warnings.
Solved by adding a header guard for the lines that actually need
to be reapplied.
- lib/vauth/digest: fix `-Wunreachable-code-break` [6].
- lib/vssh/libssh2: fix `-Wunreachable-code-break` and delete redundant
block.
- lib/vtls/sectransp: fix `-Wunreachable-code-break` [7].
- lib/vtls/sectransp: suppress `-Wunreachable-code`.
Detected in `else` branches of dynamic feature checks, with results
known at compile-time, e.g.
```c
if(SecCertificateCopySubjectSummary) /* -> true */
```
Likely fixable as a separate micro-project, but given SecureTransport
is deprecated anyway, let's just silence these locally.
- src/tool_help: delete duplicate declaration for `helptext`.
- src/tool_xattr: fix `-Wunreachable-code`.
- tests: delete duplicate declaration for `unitfail` [8].
- tests: delete duplicate declaration for `strncasecompare`.
- tests/libtest: delete duplicate declaration for `gethostname`.
Originally added in 687df5c8c39c370a59999b9afc0917d808d978b7
(2010-08-02).
Got complicated later: c49e9683b85ba9d12cbb6eebc4ab2c8dba68fbdc
If there are still systems around with warnings, we may restore the
prototype, but limited for those systems.
- tests/lib2305: delete duplicate declaration for
`libtest_debug_config`.
- tests/h2-download: fix `-Wunreachable-code-break`.

[1] https://github.com/ngtcp2/nghttp3/blob/a70edb08e954d690e8fb2c1df999b5a056f8bf9f/cmake/PickyWarningsC.cmake
[2] https://ci.appveyor.com/project/curlorg/curl/builds/48553586/job/3qkgjauiqla5fj45?fullLog=true#L1675
[3] https://github.com/curl/curl/actions/runs/6880886309/job/18716044703?pr=12331#step:7:72
https://github.com/curl/curl/actions/runs/6883016087/job/18722707368?pr=12331#step:7:109
[4] https://ci.appveyor.com/project/curlorg/curl/builds/48555101/job/9g15qkrriklpf1ut#L204
[5] https://ci.appveyor.com/project/curlorg/curl/builds/48555101/job/9g15qkrriklpf1ut#L218
[6] https://github.com/curl/curl/actions/runs/6880886309/job/18716042927?pr=12331#step:7:290
[7] https://github.com/curl/curl/actions/runs/6891484996/job/18746659406?pr=12331#step:9:1193
[8] https://github.com/curl/curl/actions/runs/6882803986/job/18722082562?pr=12331#step:33:1870

Closes #12331

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autotools: stop setting `-std=gnu89` with `--enable-warnings`

Do not alter the C standard when building with `--enable-warnings` when
building with gcc.

On one hand this alters

autotools: stop setting `-std=gnu89` with `--enable-warnings`

Do not alter the C standard when building with `--enable-warnings` when
building with gcc.

On one hand this alters warning results compared to a default build.
On the other, it may produce different binaries, which is unexpected.

Also fix new warnings that appeared after removing `-std=gnu89`:

- include: fix public curl headers to use the correct printf mask for
`CURL_FORMAT_CURL_OFF_T` and `CURL_FORMAT_CURL_OFF_TU` with mingw-w64
and Visual Studio 2013 and newer. This fixes the printf mask warnings
in examples and tests. E.g. [1]

- conncache: fix printf format string [2].

- http2: fix potential null pointer dereference [3].
(seen on Slackware with gcc 11.)

- libssh: fix printf format string in SFTP code [4].
Also make MSVC builds compatible with old CRT versions.

- libssh2: fix printf format string in SFTP code for MSVC.
Applying the same fix as for libssh above.

- unit1395: fix `argument is null` and related issues [5]:
- stop calling `strcmp()` with NULL to avoid undefined behaviour.
- fix checking results if some of them were NULL.
- do not pass NULL to printf `%s`.

- ci: keep a build job with `-std=gnu89` to continue testing for
C89-compliance. We can apply this to other gcc jobs as needed.
Ref: b23ce2cee7329bbf425f18b49973b7a5f23dfcb4 (2022-09-23) #9542

[1] https://dev.azure.com/daniel0244/curl/_build/results?buildId=18581&view=logs&jobId=ccf9cc6d-2ef1-5cf2-2c09-30f0c14f923b
[2] https://github.com/curl/curl/actions/runs/6896854263/job/18763831142?pr=12346#step:6:67
[3] https://github.com/curl/curl/actions/runs/6896854253/job/18763839238?pr=12346#step:30:214
[4] https://github.com/curl/curl/actions/runs/6896854253/job/18763838007?pr=12346#step:29:895
[5] https://github.com/curl/curl/actions/runs/6896854253/job/18763836775?pr=12346#step:33:1689

Closes #12346

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autotools: fix/improve gcc and Apple clang version detection

- Before this patch we expected `n.n` `-dumpversion` output, but Ubuntu
may return `n-win32` (also with `-dumpfullversion`)

autotools: fix/improve gcc and Apple clang version detection

- Before this patch we expected `n.n` `-dumpversion` output, but Ubuntu
may return `n-win32` (also with `-dumpfullversion`). Causing these
errors and failing to enable picky warnings:
```
../configure: line 23845: test: : integer expression expected
```
Ref: https://github.com/libssh2/libssh2/actions/runs/6263453828/job/17007893718#step:5:143

Fix that by stripping any dash-suffix and handling a dotless (major-only)
version number by assuming `.0` in that case.

`9.3-posix`, `9.3-win32`, `6`, `9.3.0`, `11`, `11.2`, `11.2.0`
Ref: https://github.com/mamedev/mame/pull/9767

- fix Apple clang version detection for releases between
'Apple LLVM version 7.3.0' and 'Apple LLVM version 10.0.1' where the
version was under-detected as 3.7 llvm/clang equivalent.

- fix Apple clang version detection for 'Apple clang version 11.0.0'
and newer where the Apple clang version was detected, instead of its
llvm/clang equivalent.

- display detected clang/gcc/icc compiler version.

Via libssh2:
- https://github.com/libssh2/libssh2/commit/00a3b88c51cdb407fbbb347a2e38c5c7d89875ad
https://github.com/libssh2/libssh2/pull/1187
- https://github.com/libssh2/libssh2/commit/89ccc83c7da73e7ca3a112e350008131942b592e
https://github.com/libssh2/libssh2/pull/1232

Closes #12362

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autotools: delete LCC compiler support bits

Follow-up to fd7ef00f4305a2919e6950def1cf83d0110a4acd #12222

Closes #12357

tidy-up: casing typos, delete unused Windows version aliases

- cmake: fix casing of `UnixSockets` to match the rest of the codebase.

- curl-compilers.m4: fix casing in a comment.

tidy-up: casing typos, delete unused Windows version aliases

- cmake: fix casing of `UnixSockets` to match the rest of the codebase.

- curl-compilers.m4: fix casing in a comment.

- setup-win32: delete unused Windows version constant aliases.

Reviewed-by: Marcel Raad
Closes #12351

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build: picky warning updates

- cmake: sync some picky gcc warnings with autotools.
- cmake, autotools: add `-Wold-style-definition` for clang too.
- cmake: more precise version info

build: picky warning updates

- cmake: sync some picky gcc warnings with autotools.
- cmake, autotools: add `-Wold-style-definition` for clang too.
- cmake: more precise version info for old clang options.
- cmake: use `IN LISTS` syntax in `foreach()`.

Reviewed-by: Daniel Stenberg
Reviewed-by: Marcel Raad
Closes #12324

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build: delete support bits for obsolete Windows compilers

- Pelles C: Unclear status, failed to obtain a fresh copy a few months
ago. Possible website is HTTP-only. ~10 years ago I lef

build: delete support bits for obsolete Windows compilers

- Pelles C: Unclear status, failed to obtain a fresh copy a few months
ago. Possible website is HTTP-only. ~10 years ago I left this compiler
dealing with crashes and other issues with no response on the forum
for years. It has seen some activity in curl back in 2021.
- LCC: Last stable release in September 2002.
- Salford C: Misses winsock2 support, possibly abandoned? Last mentioned
in 2006.
- Borland C++: We dropped Borland C++ support in 2018.
- MS Visual C++ 6.0: Released in 1998. curl already requires VS 2010
(or possibly 2008) as a minimum.

Closes #12222

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autotools: sync up clang picky warnings with cmake

Bringing missing options over from CMake.

Move around existing `-Wno-pointer-bool-conversion` option to come
_after_ `-Wconver

autotools: sync up clang picky warnings with cmake

Bringing missing options over from CMake.

Move around existing `-Wno-pointer-bool-conversion` option to come
_after_ `-Wconversion`.

Reviewed-by: Marcel Raad
Closes #10974

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