... and a minor wording edit

Dennis Clarke from Blastwave.org for ensuring that nightly builds run
smooth on Solaris!

When enabling CURLOPT_NOBODY, libcurl effectively switches off upload
mode and will do a download (without a body). This is now better
explained in this man page.

Bug: http://curl.haxx.se/mail/lib-2014-08/0236.html
Reported-by: John Coffey

I re-ran contributors.sh on all changes since 7.10 and I found these
contributors who are mentioned in the commits but never were added to
THANKS before!

I also removed a couple of duplicates (mostly due to different
spellings).

Bug: http://curl.haxx.se/bug/view.cgi?id=1414
Reported-by: teo8976

Problem: if CURLOPT_FORBID_REUSE is set, requests using NTLM failed
since NTLM requires multiple requests that re-use the same connection
for the authentication to work

Solution: Ignore the forbid reuse flag in case the NTLM authentication
handshake is in progress, according to the NTLM state flag.

Fixed known bug #77.

Updated "FTP 4.6 GSSAPI via Windows SSPI" and "SASL 14.1 Other
authentication mechanisms" following recent additions.

Added SASL 14.2 GSSAPI via GSS-API libraries.

This repeats what has already been documented in both the curl manpage
and CURLOPT_USERPWD documentation but is provided here for completeness
as someone may not especially read the latter when using libcurl.

Added information about Kerberos V5 requiring the domain part in the
user name.

Mentioned that the user name can be specified in UPN format, and not
just in Down-Level Logon Name format, following the information
added in commit 7679cb3f reworking the exisitng information in the
process.

Bug: http://curl.haxx.se/mail/lib-2014-07/0335.html
Reported-by: David Shaw

Reflect recent changes in SPNEGO and GSS-API code in the docs.
Update them with appropriate namings and remove visible spots for
GSS-Negotiate.

... and has been so since 2005

Each backend now defines CURL_SSL_BACKEND accordingly. Added the *AXTLS
one which was missing previously.

... with permission from David Shaw

1 - fixes the warnings when built without http2 support

2 - adds CURLE_HTTP2, a new error code for errors detected by nghttp2
basically when they are about http2 specific things.