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.

There was a mismatch in function parameter names.

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.

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.

Previously if HTTP/2 traffic is appended to HTTP Upgrade response header
(thus they are in the same buffer), the trailing HTTP/2 traffic is not
processed and lost.  The appended data is most likely SETTINGS frame.
If it is lost, nghttp2 library complains server does not obey the HTTP/2
protocol and issues GOAWAY frame and curl eventually drops connection.
This commit fixes this problem and now trailing data is processed.

It isn't used anywhere!

Reported-by: Carlo Wood

Fix detection of the AsynchDNS feature which not just depends on
pthreads support, but also on whether USE_POSIX_THREADS is set or not.
Caught by test 1014.

This patch adds a new ENABLE_THREADED_RESOLVER option (corresponding to
--enable-threaded-resolver of autotools) which also needs a check for
HAVE_PTHREAD_H.

For symmetry with autotools, CURL_USE_ARES is renamed to ENABLE_ARES
(--enable-ares). Checks that test for the availability actually use
USE_ARES instead as that is the result of whether a-res is available or
not (in practice this does not matter as CARES is marked as required
package, but nevertheless it is better to write the intent).

Signed-off-by: Peter Wu <peter@lekensteyn.nl>

vtls.c:185:46: warning: unused parameter 'data'

In preparation for moving the NTLM message code into the SASL module,
and separating the native code from the SSPI code, added functions that
simply call the functions in curl_ntlm_msg.c.

In preparation for moving the NTLM message code into the SASL module
use the SASL functions in the HTTP code instead.

... so that non-configure builds get the correct functions too based on
the libssh2 version used.

... if the libssh2 version is new enough.

Bug: http://curl.haxx.se/bug/view.cgi?id=1448

USE_NTLM would only be defined if: HTTP support was enabled, NTLM and
cryptography weren't disabled, and either a supporting cryptography
library or Windows SSPI was being compiled against.

This means it was not possible to build libcurl without HTTP support
and use NTLM for other protocols such as IMAP, POP3 and SMTP. Rather
than introduce a new SASL pre-processor definition, removed the HTTP
prerequisite just like USE_SPNEGO and USE_KRB5.

Note: Winbind support still needs to be dependent on CURL_DISABLE_HTTP
as it is only available to HTTP at present.

This bug dates back to August 2011 when I started to add support for
NTLM to SMTP.

Due to commit 40ee1ba0 the free in Curl_ntlm_decode_type2_target() is
longer required.

Fixed a couple of memory leaks as a result of moving code that used to
populate allocuserpwd and relied on it's clean up.

Following the addition of SSPI support for HTTP digest, synchronised
elements of the email digest code with that of the new HTTP code.

Post tidy up to ensure commonality of code style and variable names.

Reworked the input token (challenge message) storage as what is passed
to the buf and desc in the response generation are typically blobs of
data rather than strings, so this is more in keeping with other areas
of the SSPI code, such as the NTLM message functions.

Added void reference to unused 'data' parameter back to fix compilation
warning.