proxy: Support HTTPS proxy and SOCKS+HTTP(s)

* HTTPS proxies:

An HTTPS proxy receives all transactions over an SSL/TLS connection.
Once a secure connection with the proxy is est

proxy: Support HTTPS proxy and SOCKS+HTTP(s)

* HTTPS proxies:

An HTTPS proxy receives all transactions over an SSL/TLS connection.
Once a secure connection with the proxy is established, the user agent
uses the proxy as usual, including sending CONNECT requests to instruct
the proxy to establish a [usually secure] TCP tunnel with an origin
server. HTTPS proxies protect nearly all aspects of user-proxy
communications as opposed to HTTP proxies that receive all requests
(including CONNECT requests) in vulnerable clear text.

With HTTPS proxies, it is possible to have two concurrent _nested_
SSL/TLS sessions: the "outer" one between the user agent and the proxy
and the "inner" one between the user agent and the origin server
(through the proxy). This change adds supports for such nested sessions
as well.

A secure connection with a proxy requires its own set of the usual SSL
options (their actual descriptions differ and need polishing, see TODO):

--proxy-cacert FILE CA certificate to verify peer against
--proxy-capath DIR CA directory to verify peer against
--proxy-cert CERT[:PASSWD] Client certificate file and password
--proxy-cert-type TYPE Certificate file type (DER/PEM/ENG)
--proxy-ciphers LIST SSL ciphers to use
--proxy-crlfile FILE Get a CRL list in PEM format from the file
--proxy-insecure Allow connections to proxies with bad certs
--proxy-key KEY Private key file name
--proxy-key-type TYPE Private key file type (DER/PEM/ENG)
--proxy-pass PASS Pass phrase for the private key
--proxy-ssl-allow-beast Allow security flaw to improve interop
--proxy-sslv2 Use SSLv2
--proxy-sslv3 Use SSLv3
--proxy-tlsv1 Use TLSv1
--proxy-tlsuser USER TLS username
--proxy-tlspassword STRING TLS password
--proxy-tlsauthtype STRING TLS authentication type (default SRP)

All --proxy-foo options are independent from their --foo counterparts,
except --proxy-crlfile which defaults to --crlfile and --proxy-capath
which defaults to --capath.

Curl now also supports %{proxy_ssl_verify_result} --write-out variable,
similar to the existing %{ssl_verify_result} variable.

Supported backends: OpenSSL, GnuTLS, and NSS.

* A SOCKS proxy + HTTP/HTTPS proxy combination:

If both --socks* and --proxy options are given, Curl first connects to
the SOCKS proxy and then connects (through SOCKS) to the HTTP or HTTPS
proxy.

TODO: Update documentation for the new APIs and --proxy-* options.
Look for "Added in 7.XXX" marks.

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curl -w: added more decimal digits to timing counters

Now showing microsecond resolution.

Closes #1106

curl_strequal: part of public API/ABI, needs to be kept

These two public functions have been mentioned as deprecated since a
very long time but since they are still part of the API and A

curl_strequal: part of public API/ABI, needs to be kept

These two public functions have been mentioned as deprecated since a
very long time but since they are still part of the API and ABI we need
to keep them around.

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strcasecompare: is the new name for strequal()

... to make it less likely that we forget that the function actually
does case insentive compares. Also replaced several invokes of the

strcasecompare: is the new name for strequal()

... to make it less likely that we forget that the function actually
does case insentive compares. Also replaced several invokes of the
function with a plain strcmp when case sensitivity is not an issue (like
comparing with "-").

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http: add CURLINFO_HTTP_VERSION and %{http_version}

Adds access to the effectively used http version to both libcurl and
curl.

Closes #799

URLs: change all http:// URLs to https://

tool: use ENABLE_CURLX_PRINTF instead of _MPRINTF_REPLACE

tool_writeout.c: initialize string pointer variable

Revert changes relative to lib/*.[ch] recent renaming

This reverts renaming and usage of lib/*.h header files done
28-12-2012, reverting 2 commits:

f871de0... build: make use

Revert changes relative to lib/*.[ch] recent renaming

This reverts renaming and usage of lib/*.h header files done
28-12-2012, reverting 2 commits:

f871de0... build: make use of 76 lib/*.h renamed files
ffd8e12... build: rename 76 lib/*.h files

This also reverts removal of redundant include guard (redundant thanks
to changes in above commits) done 2-12-2013, reverting 1 commit:

c087374... curl_setup.h: remove redundant include guard

This also reverts renaming and usage of lib/*.c source files done
3-12-2013, reverting 3 commits:

13606bb... build: make use of 93 lib/*.c renamed files
5b6e792... build: rename 93 lib/*.c files
7d83dff... build: commit 13606bbfde follow-up 1

Start of related discussion thread:

http://curl.haxx.se/mail/lib-2013-01/0012.html

Asking for confirmation on pushing this revertion commit:

http://curl.haxx.se/mail/lib-2013-01/0048.html

Confirmation summary:

http://curl.haxx.se/mail/lib-2013-01/0079.html

NOTICE: The list of 2 files that have been modified by other
intermixed commits, while renamed, and also by at least one
of the 6 commits this one reverts follows below. These 2 files
will exhibit a hole in history unless git's '--follow' option
is used when viewing logs.

lib/curl_imap.h
lib/curl_smtp.h

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writeout: -w now supports remote_ip/port and local_ip/port

Added mention to the curl.1 man page.

Test case 1223 verifies remote_ip/port.

build: make use of 76 lib/*.h renamed files

76 private header files renamed to use our standard naming scheme.

This change affects 322 files in libcurl's source tree.

curl tool: make curl.h first header included in tool_setup.h

curl tool: use configuration files from lib directory

Configuration files such as curl_config.h and all config-*.h no longer exist
nor are generated/copied into 'src' directory, now thes

curl tool: use configuration files from lib directory

Configuration files such as curl_config.h and all config-*.h no longer exist
nor are generated/copied into 'src' directory, now these only exist in 'lib'
directory from where curl tool sources uses them.

Additionally old src/setup.h has been refactored into src/tool_setup.h which
now pulls lib/setup.h

The possibility of a makefile needing an include path adjustment exists.

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curl tool: add filename_effective token for --write-out

By modifying the parameter list for ourWriteOut() and passing the
OutStruct that collects data in tool_operate, we get access to t

curl tool: add filename_effective token for --write-out

By modifying the parameter list for ourWriteOut() and passing the
OutStruct that collects data in tool_operate, we get access to the
remote name that we're writing to. Shell scripters should find this
useful when used in conjuntion with the --remote-header-name option.

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curl tool: reviewed code moved to tool_*.[ch] files