Prior to this change when no file descriptors were ready on platforms
other than Windows the multi examples would sleep whatever was in
timeout, which may or may not have been less than the minimum
recommended value [1] of 100ms.

[1]: http://curl.haxx.se/libcurl/c/curl_multi_fdset.html

When the connection code decides to close a socket it informs the multi
system via the Curl_multi_closed function. The multi system may, in
turn, invoke the CURLMOPT_SOCKETFUNCTION function with
CURL_POLL_REMOVE. This happens after the socket has already been
closed. Reorder the code so that CURL_POLL_REMOVE is called before the
socket is closed.

Moved target autodetection block after defining CC macro.

Remove use of an old hack that takes advantage of the auto-dereference
behavior of the if() command to detect if a variable is defined.  The
hack has the form:

 if("${VAR} MATCHES "^${VAR}$")

where "${VAR}" is a macro argument reference.  Use if(DEFINED) instead.
This also avoids warnings for CMake Policy CMP0054 in CMake 3.1.

Debug output 'typo' fix.

Don't print an extra "0x" in
  * Pipe broke: handle 0x0x2546d88, url = /

Add debug output.
Print the number of connections in the connection cache when
  adding one, and not only when one is removed.

Fix typos in comments.

... as it was before I changed the loop in commit e04ccbd5. It caused
test 2030 and 2032 to fail.

... and assign data->result only at the end. Makes the code more compact
(easier to read) and more similar to other code.

save 'result' for CURLcode types

simplifies the use of this function at little cost.

Fixes the problem when a transfer in a pipeline times out.

Even though commit 23e70e1c mentioned the v110_xp toolset, I had
forgotten to include the relevant pre-processor definitions.

warning: unused parameter 'reason'

warning: unused parameter 'easy'

Updated the usage of some legacy APIs, that are preventing curl from
compiling for Windows Store and Windows Phone build targets.

Suggested-by: Stefan Neis
Feature: http://sourceforge.net/p/curl/feature-requests/82/

Visual Studio 2012 introduced support for Windows Store apps as well as
supporting Windows Phone 8. Introduced build targets that allow more
modern APIs to be used as certain legacy ones are not available on these
new platforms.

Just like in the NTLM code, added infof() failure messages for
DIGEST-MD5 and GSSAPI authentication when base64 decoding fails.

For consistency renamed USE_KRB5 to USE_KERBEROS5.

Windows does not support using select() for sleeping without a dummy
socket. Instead use Windows' Sleep() and sleep for 100ms which is the
minimum suggested value in the curl_multi_fdset() doc.

Prior to this change the multi examples would exit prematurely since
select() would error instead of sleeping when called without an fd.

Reported-by: Johan Lantz
Bug: http://curl.haxx.se/mail/lib-2014-11/0221.html

There was a mismatch in function parameter names.

Although libcurl would never return CURL_VERSION_KERBEROS4 after 7.33,
so would not be output with --version, removed krb4 from the supported
features output.

This variable is only used with HAVE_GSSAPI is defined by the FTP code
so let's place the definition with the other GSS-API based variables.