cmake: fix `-Wredundant-decls` in unity/mingw-w64/gcc/curldebug/DLL builds

It affected cmake-unity shared-curltool curldebug mingw-w64 gcc builds
when building the `testdeps` target.

cmake: fix `-Wredundant-decls` in unity/mingw-w64/gcc/curldebug/DLL builds

It affected cmake-unity shared-curltool curldebug mingw-w64 gcc builds
when building the `testdeps` target.

Apply the solution already used in `lib/base64.c` and `lib/dynbuf.c`
to fix it.

Also update an existing GHA CI job to test the issue fixed.

```
In file included from curl/lib/version_win32.c:35,
from curl/_bld/src/CMakeFiles/curl.dir/Unity/unity_0_c.c:145:
curl/lib/memdebug.h:52:14: error: redundant redeclaration of 'curl_dbg_logfile' [-Werror=redundant-decls]
52 | extern FILE *curl_dbg_logfile;
| ^~~~~~~~~~~~~~~~
In file included from curl/src/slist_wc.c:32,
from curl/_bld/src/CMakeFiles/curl.dir/Unity/unity_0_c.c:4:
curl/lib/memdebug.h:52:14: note: previous declaration of 'curl_dbg_logfile' with type 'FILE *' {aka 'struct _iobuf *'}
52 | extern FILE *curl_dbg_logfile;
| ^~~~~~~~~~~~~~~~
curl/lib/memdebug.h:55:44: error: redundant redeclaration of 'curl_dbg_malloc' [-Werror=redundant-decls]
55 | CURL_EXTERN ALLOC_FUNC ALLOC_SIZE(1) void *curl_dbg_malloc(size_t size,
| ^~~~~~~~~~~~~~~
curl/lib/memdebug.h:55:44: note: previous declaration of 'curl_dbg_malloc' with type 'void *(size_t, int, const char *)' {aka 'void *(long long unsigned int, int, const char *)'}
55 | CURL_EXTERN ALLOC_FUNC ALLOC_SIZE(1) void *curl_dbg_malloc(size_t size,
| ^~~~~~~~~~~~~~~
[...]
curl/lib/memdebug.h:110:17: error: redundant redeclaration of 'curl_dbg_fclose' [-Werror=redundant-decls]
110 | CURL_EXTERN int curl_dbg_fclose(FILE *file, int line, const char *source);
| ^~~~~~~~~~~~~~~
curl/lib/memdebug.h:110:17: note: previous declaration of 'curl_dbg_fclose' with type 'int(FILE *, int, const char *)' {aka 'int(struct _iobuf *, int, const char *)'}
110 | CURL_EXTERN int curl_dbg_fclose(FILE *file, int line, const char *source);
| ^~~~~~~~~~~~~~~
```
Ref: https://ci.appveyor.com/project/curlorg/curl/builds/49840554/job/a4aoet17e9qnqx1a#L362

After: https://ci.appveyor.com/project/curlorg/curl/builds/49843735/job/hbo2uah2vj0ns523

Ref: #13689 (CI testing this PR with `DEBUGBUILD`/`CURLDEBUG`/shared-static combinations)
Depends-on: #13694
Depends-on: #13800
Closes #13705

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lib: fix gcc warning in certain debug builds

```
curl/lib/http_aws_sigv4.c:536:10: error: 'clock' may be used uninitialized [-Werror=maybe-uninitialized]
536 | time_t clock;

lib: fix gcc warning in certain debug builds

```
curl/lib/http_aws_sigv4.c:536:10: error: 'clock' may be used uninitialized [-Werror=maybe-uninitialized]
536 | time_t clock;
| ^~~~~
```
Ref: https://github.com/curl/curl/actions/runs/9158755123/job/25177765000#step:13:79

Cherry-picked from #13718
Closes #13800

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cmake: always build unit tests with the `testdeps` target

Before this patch, the `testdeps` build target required `-DCURLDEBUG`
be set either via `ENABLE_DEBUG=ON` or `ENABLE_CURLDEBUG=O

cmake: always build unit tests with the `testdeps` target

Before this patch, the `testdeps` build target required `-DCURLDEBUG`
be set either via `ENABLE_DEBUG=ON` or `ENABLE_CURLDEBUG=ON` to build
the curl unit tests.

After fixing build issues in #13694, we can drop this requirement and
build unit tests unconditionally.

Depends-on: #13694
Depends-on: #13697 (fix unit test issue revealed by Old Linux CI job)
Follow-up to 39e7c22bb459c2e818f079984989a26a09741860 #11446
Closes #13698

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CI: disable dependency tracking in most autotools builds

For better build performance. Dependency tracking causes a build
overhead while compiling to help a subsequent build, but in CI t

CI: disable dependency tracking in most autotools builds

For better build performance. Dependency tracking causes a build
overhead while compiling to help a subsequent build, but in CI there is
never one and the extra work is discarded.

Closes #13794

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build: untangle `UNITTESTS` and `DEBUGBUILD` macros

- fix `DEBUGBUILD` guards that should be `UNITTESTS`, in libcurl code
used by unit tests.
- fix guards for libcurl functions use

build: untangle `UNITTESTS` and `DEBUGBUILD` macros

- fix `DEBUGBUILD` guards that should be `UNITTESTS`, in libcurl code
used by unit tests.
- fix guards for libcurl functions used in unit tests only.
- sync `UNITTEST` attribute between declarations and definitions.
- drop `DEBUGBUILD` guard from test `unit2600`.
- fix guards for libcurl HSTS code used by both a unit test (`unit1660`)
and `test0446`.
- update an existing AppVeyor CI job to test the issues fixed.

This fixes building tests with `CURLDEBUG` enabled but `DEBUGBUILD`
disabled. This can happen when building tests with CMake with
`ENABLE_DEBUG=ON` in Release config, or with `ENABLE_CURLDEBUG=ON`
and _without_ `ENABLE_DEBUG=ON`. Possibly also with autotools
when using `--enable-curldebug` without `--enable-debug`.

Test results:
- before:
https://ci.appveyor.com/project/curlorg/curl/builds/49835609
https://ci.appveyor.com/project/curlorg/curl/builds/49898529/job/k8qpbs8idby70smw
https://github.com/curl/curl/actions/runs/9259078835/job/25470318167?pr=13798#step:13:821
- after: https://ci.appveyor.com/project/curlorg/curl/builds/49839255
(the two failures are unrelated, subject to PR #13705)

Ref: #13592 (issue discovery)
Ref: #13689 (CI testing this PR with `DEBUGBUILD`/`CURLDEBUG` combinations)
Closes #13694

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GHA: ignore flaky MQTT and FTP test results [ci skip]

MQTT / OmniOS:
```
TESTFAIL: These test cases failed: 1190 1198 3017
```
Ref: https://github.com/curl/curl/actions/runs/

GHA: ignore flaky MQTT and FTP test results [ci skip]

MQTT / OmniOS:
```
TESTFAIL: These test cases failed: 1190 1198 3017
```
Ref: https://github.com/curl/curl/actions/runs/9258522297/job/25468730731?pr=13694#step:3:10251

MQTT / OmniOS:
```
TESTFAIL: These test cases failed: 1194 2200 2203 2205
```
Ref: https://github.com/curl/curl/actions/runs/9150523540/job/25155409832#step:3:10233

FTP / OmniOS:
```
TESTFAIL: These test cases failed: 1096
```
Ref: https://github.com/curl/curl/actions/runs/9150702711/job/25155793948#step:3:10247

FTP / OmniOS:
```
TESTFAIL: These test cases failed: 381
```
Ref: https://github.com/curl/curl/actions/runs/9163863822/job/25193897640#step:3:10230

FTP / OmniOS:
```
TESTFAIL: These test cases failed: 340
```
Ref: https://github.com/curl/curl/actions/runs/9233804752/job/25406671742?pr=13771#step:3:10245

Ref: https://github.com/curl/curl/pull/13583#issuecomment-2119376898

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CI: tidy up skipping tests build/run in Windows jobs

Simplify controlling whether to build and/run tests in a CI job.

Apply the TFLAGS='skipall' (do not build nor run tests) or

CI: tidy up skipping tests build/run in Windows jobs

Simplify controlling whether to build and/run tests in a CI job.

Apply the TFLAGS='skipall' (do not build nor run tests) or
'skiprun' (build, but do not run) method already used with old-mingw-w64
and msvc jobs to existing Windows jobs in GHA and AppVeyor.

Also:
- add Cygwin/cmake test build and run steps while here.
- replace `DISABLED_TESTS` with `TFLAGS` in AppVeyor.

Closes #13796

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cmake: use `APPLE` instead of `CMAKE_SYSTEM_NAME` string

Follow-up to a86254b39307af1a53735b065a382567805cd9b8 #12515
Closes #13713

cmake: whitespace, formatting/tidy-up in comments

Also correct casing in a few option descriptions.

Closes #13711

cmake: allow `ENABLE_CURLDEBUG=OFF` with `ENABLE_DEBUG=ON`

Before this patch, `ENABLE_CURLDEBUG` (memory tracking) was
unconditionally enabled when `ENABLE_DEBUGBUILD` was set. This made

cmake: allow `ENABLE_CURLDEBUG=OFF` with `ENABLE_DEBUG=ON`

Before this patch, `ENABLE_CURLDEBUG` (memory tracking) was
unconditionally enabled when `ENABLE_DEBUGBUILD` was set. This made
testing some build configurations complicated. To fix it, this patch
makes `ENABLE_CURLDEBUG` to receive the value of `ENABLE_DEBUG` by
default, while allowing free override by the user.

This allows to use the config:
`ENABLE_DEBUGBUILD=ON ENABLE_CURLDEBUG=OFF`
to enable debug features, without also enabling memory tracking.

This is important because some other build methods allow to set one of
these features but not the other. This patch allows to test any
combination with CMake.

This makes it unnecessary to use the workaround of passing
`-DDEBUGBUILD` via `CMAKE_C_FLAGS`. Which has the disadvantage that our
CMake logic cannot easily detect it, e.g. for disabling symbol hiding on
Windows for `ENABLE_DEBUG`/`DEBUGBUILD` builds.

Cherry-picked from #13718
Closes #13792

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cmake: `ENABLE_DEBUG=ON` to always set `-DDEBUGBUILD`

Before this patch `ENABLE_DEBUG=ON` always enabled the TrackMemory
(aka `ENABLE_CURLDEBUG=ON`) feature, but required the `Debug` CMa

cmake: `ENABLE_DEBUG=ON` to always set `-DDEBUGBUILD`

Before this patch `ENABLE_DEBUG=ON` always enabled the TrackMemory
(aka `ENABLE_CURLDEBUG=ON`) feature, but required the `Debug` CMake
configration to actually enable curl debug features
(aka `-DDEBUGBUILD`).

Curl debug features do not require compiling with C debug options. This
also made enabling debug features unintuitive and complicated to use.
Due to other issues (subject to PR #13694) it also caused an error in
default (and `Release`/`MinSizeRel`/`RelWithDebInfo`) configs, when
building the `testdeps` target:
```
ld: CMakeFiles/unit1395.dir/unit1395.c.o: in function `test':
unit1395.c:(.text+0x1a0): undefined reference to `dedotdotify'
```
Ref: https://github.com/curl/curl/actions/runs/9037287098/job/24835990826#step:3:2483

Fix it by always defining `DEBUGBUILD` when setting `ENABLE_DEBUG=ON`.
Decoupling this option from the selected CMake configuration.

Note that after this patch `ENABLE_DEBUG=ON` unconditionally enables
curl debug features. These features are insecure and unsuited for
production. Make sure to omit this option when building for production
in default, `Release` (and other not-`Debug`) modes.

Also delete a workaround no longer necessary in GHA CI jobs.

Ref: 1a62b6e68c08c7e471ff22dd92932aba7e026817 (2015-03-03)
Ref: #13583
Closes #13592

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GHA: add autotools mingw-64, build-only job

Cherry-picked from #13718
Closes #13793

GHA: add three MSVC jobs

Continuing the theme, add 3 MSVC jobs with tests, matching
configurations used on AppVeyor. MSVC versions are identical:
19.39.33523.0 + Windows SDK 10.0.226

GHA: add three MSVC jobs

Continuing the theme, add 3 MSVC jobs with tests, matching
configurations used on AppVeyor. MSVC versions are identical:
19.39.33523.0 + Windows SDK 10.0.22621.0.

Also enable websockets, and build examples. Tests are run in parallel
(`-j14`), with improved performance.

Job performance:
```
AppVeyor GHA
w/examples
-------- ----------
CMake, VS2022, Debug, x64, Schannel, Static, Unicode 38m 4s 11m57s
CMake, VS2022, Debug, x64, no SSL, Static 35m15s 12m 6s
CMake, VS2022, Debug, x64, no SSL, Static, HTTP only 25m25s 10m36s
```
Based on these runs:
https://ci.appveyor.com/project/curlorg/curl/builds/49884748
https://github.com/curl/curl/actions/runs/9229448468

This is the first time examples are built in CI with MSVC: Fix all
warnings and errors that came up via
d4b85890555388bec212b75f47a5c1a48705b156 #13771.

Closes #13766

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GHA: add three old (gcc 6, 7, 9) mingw-w64 jobs

Re-implement old mingw-w64 jobs in GHA. This allows to use the latest
Windows runners, replacing Windows Server 2012 R2 (gcc 6) and Window

GHA: add three old (gcc 6, 7, 9) mingw-w64 jobs

Re-implement old mingw-w64 jobs in GHA. This allows to use the latest
Windows runners, replacing Windows Server 2012 R2 (gcc 6) and Windows
Server 2016 (gcc 7, 9) with Windows Server 2022.

GHA runners are also significantly faster, and allow running tests in
parallel (`-j14`). It also offloads 3 more long-running jobs from
AppVeyor CI.

These jobs download (then cache) the mingw-w64 packages from their
original location, which allows flexibility in choosing which versions
and flavours (win32/POSIX, SEH/DWARF, 64/32-bit) we want to test in CI.
The new jobs use these distros:
- https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/ (for gcc 7, same as on AppVeyor)
- https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/ (for gcc 6, same as on AppVeyor)
- https://winlibs.com/ (for gcc 9)

I matched existing AppVeyor job configs, with these differences:
- gcc 6.4.0 instead of 6.3.0.
(same distro as on AppVeyor, but the latest bugfix release)
- gcc 9.5.0 instead of 9.1.0 and a different (but compatible) binary distro.
(in AppVeyor this relies on an old MSYS2 pre-installed on the runner)
- using win32 builds instead of posix for gcc 6.4.0 and 7.3.0.
- websockets enabled.
- always build examples.
- always build tests (this wasn't done for 6.4.0 with AppVeyor CI).

I did not replicate existing test exclusions, and oddly enough the few
failures (so far) were different from MSYS2 jobs and also from their
AppVeyor CI counterparts.

Also:
- delete redundant (default) `-u` option from `cygpath` calls.
- allow matrix options to override default ones in CMake.
- detect and use Windows-supplied curl for `TFLAGS` `-ac` option.
(it's available in modern runners.)
- delete the 3 AppVeyor CI jobs now replicated in GHA.
- appveyor: prefer `SYSTEMROOT` over `WINDIR`.
- tidy-up quotes.

Job performance:
```
AppVeyor GHA
w/examples
w/tests
-------- ----------
CMake, mingw-w64, gcc 6, Debug, x86, Schannel, Static, no-unity 1m25s 8m50s
CMake, mingw-w64, gcc 7, Debug, x64, Schannel, Static, Unicode 31m45s 9m39s
CMake, mingw-w64, gcc 9, Debug, x64, Schannel, Static 28m25s 13m38s
```
Based on these runs:
https://ci.appveyor.com/project/curlorg/curl/builds/49880799
https://github.com/curl/curl/actions/runs/9218292508

Notice that building examples and tests is time consuming.

We can tweak any build parameter as necessary to make them more useful
and/or without clogging the job queue or introducing flakiness.

Closes #13759

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TODO: remove some old, clarify, add something

Closes #13788

TODO: Add "Share CA cache" + "CA caching to more TLS backends"

Closes #13787

runtests: sort test IDs in summary lines

Changing this output:
```
TESTFAIL: These test cases failed: 2301 2303 2302 2307
```
Ref: https://github.com/curl/curl/actions/runs/9

runtests: sort test IDs in summary lines

Changing this output:
```
TESTFAIL: These test cases failed: 2301 2303 2302 2307
```
Ref: https://github.com/curl/curl/actions/runs/9228638364/job/25393106631#step:6:21181

To:
```
TESTFAIL: These test cases failed: 2301 2302 2303 2307
```

Cherry-picked from #13766
Closes #13774

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examples: fix compiling with MSVC

- `websocket.c`: use `Sleep()` on Windows.
`sleep()` and `unistd.h` are not available in MSVC.

- `http2-upload.c`: use local `gettimeofday()`

examples: fix compiling with MSVC

- `websocket.c`: use `Sleep()` on Windows.
`sleep()` and `unistd.h` are not available in MSVC.

- `http2-upload.c`: use local `gettimeofday()` implementation when
compiled with MSVC.
(Alternate solution is to disable the trace function for MSVC.)
Public domain code copied and adapted from libssh2:
https://github.com/libssh2/libssh2/blob/e973493f992313b3be73f51d3f7ca6d52e288558/src/misc.c#L719-L743

- silence compiler warning for deprecated `inet_addr()`.
Also drop duplicate winsock2 include.
```
curl\docs\examples\externalsocket.c(125,32): error C2220: the following warning is treated as an error [curl\bld\docs\examples\curl-example-externalsocket.vcxproj]
curl\docs\examples\externalsocket.c(125,32): warning C4996: 'inet_addr': Use inet_pton() or InetPton() instead or define _WINSOCK_DEPRECATED_NO_WARNINGS to disable deprecated API warnings [curl\bld\docs\examples\curl-example-e
```
Ref: https://github.com/curl/curl/actions/runs/9227337318/job/25389073450#step:4:95

- silence an MSVC compiler warning. This is in conflict with `checksrc`
rules, so silence the rule in favour of the warning-free C syntax.
```
curl\docs\examples\multi-legacy.c(152,1): error C2220: the following warning is treated as an error [curl\bld\docs\examples\curl-example-multi-legacy.vcxproj]
curl\docs\examples\multi-legacy.c(152,1): warning C4706: assignment within conditional expression [curl\bld\docs\examples\curl-example-multi-legacy.vcxproj]
```
Ref: https://github.com/curl/curl/actions/runs/9227337318/job/25389073450#step:4:226

- do not use `sys/time.h` and `unistd.h` in Windows builds.
Some of these includes look unnecessary. Subject to another PR.

Cherry-picked from #13766
Closes #13771

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docs/cmdline-opts: fix mail-auth example TLD typo

Closes: #13784
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>

libssh: remove CURLOPT_SSL_VERIFYHOST check

It was never meant for SSH: it should rely on the knownhosts file (if
set) in the same way libssh2 already does.

Reported-by: James A

libssh: remove CURLOPT_SSL_VERIFYHOST check

It was never meant for SSH: it should rely on the knownhosts file (if
set) in the same way libssh2 already does.

Reported-by: James Abbatiello
Fixes #13767
Closes #13781

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multi: add multi->proto_hash, a key-value store for protocol data

- add `Curl_hash_add2()` that passes a destructor function for
the element added. Call element destructor instead of h

multi: add multi->proto_hash, a key-value store for protocol data

- add `Curl_hash_add2()` that passes a destructor function for
the element added. Call element destructor instead of hash
destructor if present.
- multi: add `proto_hash` for protocol related information,
remove `struct multi_ssl_backend_data`.
- openssl: use multi->proto_hash to keep x509 shared store
- schannel: use multi->proto_hash to keep x509 shared store
- vtls: remove Curl_free_multi_ssl_backend_data() and its
equivalents in the TLS backends

Closes #13345

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tests: add pytest for --ciphers and --tls13-ciphers options

Closes #13530

tool_operate: avoid explicitly setting verifypeer to 1

Also for the proxy verison. It is the default, just like verifyhost,
since a long time.

Closes #13704

tests: extend user/password parsing test1620

Closes #13756

configure: use `$EGREP` in place of `grep -E`

`$EGREP` is set based on an earlier test in configure so that we can
work with systems that have `egrep` and a `grep` that does not support

configure: use `$EGREP` in place of `grep -E`

`$EGREP` is set based on an earlier test in configure so that we can
work with systems that have `egrep` and a `grep` that does not support
`-E`.

Closes #13780

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