Relies on CURLOPT_SSL_CTX_FUNCTION, which is OpenSSL specific

... so that it adheres to the API documentation.

Reported by: Tomas Mlcoch

No API change involved.

Info: http://curl.haxx.se/mail/lib-2013-02/0234.html

Patch by: Myk Taylor

No more use exit(3) but instead tell libcurl that no byte has been
written to let it return a `CURLE_WRITE_ERROR`. In addition, check
curl easy handle return code.

Added CURLOPT_FOLLOWLOCATION since example.com is now redirected.

Added CURLOPT_FOLLOWLOCATION since example.com is now redirected.

This commit renames lib/setup.h to lib/curl_setup.h and
renames lib/setup_once.h to lib/curl_setup_once.h.

Removes the need and usage of a header inclusion guard foreign
to libcurl. [1]

Removes the need and presence of an alarming notice we carried
in old setup_once.h [2]

----------------------------------------

1 - lib/setup_once.h used __SETUP_ONCE_H macro as header inclusion guard
    up to commit ec691ca3 which changed this to HEADER_CURL_SETUP_ONCE_H,
    this single inclusion guard is enough to ensure that inclusion of
    lib/setup_once.h done from lib/setup.h is only done once.

    Additionally lib/setup.h has always used __SETUP_ONCE_H macro to
    protect inclusion of setup_once.h even after commit ec691ca3, this
    was to avoid a circular header inclusion triggered when building a
    c-ares enabled version with c-ares sources available which also has
    a setup_once.h header. Commit ec691ca3 exposes the real nature of
    __SETUP_ONCE_H usage in lib/setup.h, it is a header inclusion guard
    foreign to libcurl belonging to c-ares's setup_once.h

    The renaming this commit does, fixes the circular header inclusion,
    and as such removes the need and usage of a header inclusion guard
    foreign to libcurl. Macro __SETUP_ONCE_H no longer used in libcurl.

2 - Due to the circular interdependency of old lib/setup_once.h and the
    c-ares setup_once.h header, old file lib/setup_once.h has carried
    back from 2006 up to now days an alarming and prominent notice about
    the need of keeping libcurl's and c-ares's setup_once.h in sync.

    Given that this commit fixes the circular interdependency, the need
    and presence of mentioned notice is removed.

    All mentioned interdependencies come back from now old days when
    the c-ares project lived inside a curl subdirectory. This commit
    removes last traces of such fact.

BLANK_AT_MAKETIME may be used in our Makefile.am files to blank
LIBS variable used in generated makefile at makefile processing
time. Doing this functionally prevents LIBS from being used for
all link targets in given makefile.

Blocking connect on the socket has been removed from opensocket
callback. opensocket just opens a new socket and gives it back to
libcurl and libcurl will take care of the connect. sockopt_callback has
also been removed, as it is no longer required.

Added an example for demonstrating the usage of curl multi interface
with boost::asio in c++

Since automake 1.12.4, the warnings are issued on running automake:

  warning: 'INCLUDES' is the old name for 'AM_CPPFLAGS' (or '*_CPPFLAGS')

Avoid INCLUDES and roll these flags into AM_CPPFLAGS.

Compile tested on:
  Ubuntu 10.04 (automake 1:1.11.1-1)
  Ubuntu 12.04 (automake 1:1.11.3-1ubuntu2)
  Arch Linux (automake 1.12.4)

Bug: http://curl.haxx.se/bug/view.cgi?id=3582407
Reported by: Oscar Norlander

It does so in a streaming manner using the "Streaming HTML parser".

... in order not to leak memory on initializing an SSL library.

Reported by: Tomas Mlcoch

It's conceivable that after the first time curl_multi_perform returns,
the outvalue still_running will be 0, but work will have been done. This
is shown by a workload of small, purely file:// based URLs. Ensure that
we always read pending messages off the multi handle by forcing the
while loop to run at least once.

... using SSH-agent

Bug: http://curl.haxx.se/bug/view.cgi?id=3559845
Reported by: Olivier Berger