ntlm: We prefer 'CURLcode result'
ntlm: Clean-up and standardisation of base64 decoding
sasl_sspi: Added missing RFC reference for HTTP Digest authentication
sasl: Moved Curl_sasl_gssapi_cleanup() definition into header file

Rather than define the function as extern in the source files that use
it, moved the function declaration into the SASL header file just like
the Digest and NTLM clean-up functions.

Additionally, added a function description comment block.
sasl_sspi: Corrected a couple of comment typos
TODO: Lets support QOP options in GSSAPI authentication
docs: Use consistent naming for Kerberos
urldata: Don't define sec_complete when no GSS-API support present

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.
tool: Use Kerberos for supported features
tool: Removed krb4 from the supported features

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.
sasl: Corrected Curl_sasl_build_spn() function description

There was a mismatch in function parameter names.
http2: Don't send Upgrade headers when we already do HTTP/2
examples: Don't call select() to sleep on windows

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
kerberos: Use symbol qualified with _KERBEROS5

For consistency renamed USE_KRB5 to USE_KERBEROS5.
ntlm: Moved the SSPI based Type-1 message generation into the SASL module
ntlm: Moved the SSPI based Type-2 message decoding into the SASL module
ntlm: Moved the SSPI based Type-3 message generation into the SASL module
sasl_sspi: Added base64 decoding debug failure messages

Just like in the NTLM code, added infof() failure messages for
DIGEST-MD5 and GSSAPI authentication when base64 decoding fails.
sasl_sspi: Fixed compilation warnings when no verbose string support
config-win32: Introduce build targets for VS2012+

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.