url.c: fix HTTP CONNECT tunnel establishment upon delayed response

Fixes initial proxy response being processed by the tunneled protocol
handler instead of the HTTP wrapper handler. This issue would trigger
upon delayed CONNECT response from the proxy.

Additionally fixes a multi interface code-path in which connections
would not time out properly.

This does not fix known bug #39.

URL: http://curl.haxx.se/mail/lib-2013-01/0191.html
always-multi: always use non-blocking internals

Remove internal separated behavior of the easy vs multi intercace.
curl_easy_perform() is now using the multi interface itself.

Several minor multi interface quirks and bugs have been fixed in the
process.

Much help with debugging this has been provided by: Yang Tse
RELEASE-NOTES: synced with c43127414d89
runtests.pl: make VPATH builds find valgrind.supp
RELEASE-NOTES: Added missing imap fix

Added missing imap fix as per commit 709b3506cd9b.
RELEASE-NOTES: add references to several bugfixes+changes
pop3.c: Fixed a problem with pop3s connections not connecting properly

Fixed an issue where Curl_ssl_connect_nonblocking() wouldn't complete
correctly and the ssldone flag wouldn't be set to true for pop3s based
connections.

Bug introduced in commit: 4ffb8a6398ed.
email: General code tidy up

Corrected some function argument definitions to maximize the 80
character line length limit and be in keeping with the curl
coding style.
curl_easy_recv.3: document return codes

Reported by: Craig Davison
Bug: http://curl.haxx.se/mail/lib-2013-01/0234.html
curl_easy_send.3: document return codes

Reported by: Craig Davison
Bug: http://curl.haxx.se/mail/lib-2013-01/0234.html
formadd: reject trying to read a directory where a file is expected

Bug: http://curl.haxx.se/mail/archive-2013-01/0017.html
Reported by: Ulrich Doehner
Makefile.inc: fix $(top_srcdir) not allowed in _SOURCES variables
pop3.c: Fixed conditional compilation of the apop response function

Extended the fix from commit 8b15c84ea91e to additionally exclude
pop3_state_apop_resp() if the CURL_DISABLE_CRYPTO_AUTH flag is
defined.
configure: autotools compatibility fixes - step I

Fix proper macro expansion order across autotools versions for
C compiler and preprocessor program checks.
xc-cc-check.m4: mark earlier variables that are to be exported
xc-cc-check.m4: avoid recursive package automake'ing breakage
FAQ: 3.22 curl -X gives me HTTP problems
xc-cc-check.m4: re-evaluate exporting and AC_SUBST'ing vars

Notes:

When running a configure script that has nested packages (for example
libcurl's configure with --enable-ares and c-ares sources embedded in
curl tree) and AC_CONFIG_SUBDIRS([nested-subdir]) machinery is used to
automatically run the nested configure script from within the parent
configure script, it happens that the nested _shell_ script will
inherit shell variables exported from the parent _shell_ script.

If for example parent configure script sets and exports LDFLAGS and LIBS
variables with proper values in order to link either a parent library or
program with a library which will be configured and built by a nested
package; It will happen that when the nested configure script runs, the
nested library does not exist yet and _any_ link-test done in the nested
configure will fail, such as those that autoconf macros perform in order
to detect existing compiler and its characteristics, the result is that
the nested configure script will fail with errors such as:

configure: error: C compiler cannot create executables

For now, we no longer export variables previously exported here.

On the other hand, AC_SUBST'ing them is appropriate and even with nested
packages each package's config.status gets its own package values.

So we reinstate AC_SUBST'ing previously AC_SUBST'ed variables.
memanalyze.pl: handle fopen() of file names with quotes
formpost: support quotes, commas and semicolon in file names

- document the double-quote and backslash need be escaped if quoting.
- libcurl formdata escape double-quote in filename by backslash.
- curl formparse can parse filename both contains '"' and ',' or ';'.
- curl now can uploading file with ',' or ';' in filename.

Bug: http://curl.haxx.se/bug/view.cgi?id=1171