And renamed all http2 references to HTTP/2 in this file

At this point I can build libcurl on windows. It provides at least the same
list of protocols as for linux build and works with our software.

They are unnecesary in modern CMake and removing them improves readability.

Undefined variables resolve to empty strings and we do not ever test if
the variable is defined thus those SETs are superfluous.

They look like some relics after changes.

One header at a time is the right way. Apart from that the output on
windows goes from:
...
-- Looking for include files I:/src/libssh2-1.4.3/include/libssh2.h, ws2tcpip.h
-- Looking for include files I:/src/libssh2-1.4.3/include/libssh2.h, ws2tcpip.h
- found
-- Looking for 3 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., wins
ock2.h
-- Looking for 3 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., wins
ock2.h - found
-- Looking for 4 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., stdi
o.h
-- Looking for 4 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., stdi
o.h - found
-- Looking for 5 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., wind
ows.h
-- Looking for 5 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., wind
ows.h - found
-- Looking for 6 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., wins
ock.h
-- Looking for 6 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., wins
ock.h - found
-- Looking for 7 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., sys/
filio.h
-- Looking for 7 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., sys/
filio.h - not found
-- Looking for 7 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., sys/
ioctl.h
-- Looking for 7 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., sys/
ioctl.h - not found
-- Looking for 7 include files I:/src/libssh2-1.4.3/include/libssh2.h, ..., sys/
resource.h
...

To much nicer:
...
-- Looking for ws2tcpip.h
-- Looking for ws2tcpip.h - found
-- Looking for winsock2.h
-- Looking for winsock2.h - found
-- Looking for stdio.h
-- Looking for stdio.h - found
-- Looking for windows.h
-- Looking for windows.h - found
-- Looking for winsock.h
-- Looking for winsock.h - found
-- Looking for sys/filio.h
-- Looking for sys/filio.h - not found
-- Looking for sys/ioctl.h
-- Looking for sys/ioctl.h - not found
-- Looking for sys/resource.h

At this point I can build libcurl with OpenSSL, OpenLDAP and LibSSH2.
Supported protocols are at least:
HTTP, HTTPS, FTP, SFTP, TFTP, LDAP, LDAPS, POP3, SMTP
(those are the ones we have regression tests for
in our product's testsuite)

They already have their defines in config.h. This makes it possible to
disable the protocols from command line during configure step.

It's by convention, for compatibility and because the comments say so.
Just mabe someone have written a test like "#if HAVE_XX==1"

CMake 2.6 is already a bit old. Many bugs have been fixed since
its release. We use 2.8 in our company and we have no intention
of polluting our environment with old software, so 2.6 would
not be tested. This shouldn't be a problem since all one need
to build CMake from source is C and C++ compiler.

This was done to make sure NTLM state that is bound to a connection
doesn't survive and gets used for the subsequent request - but
disconnects can also be done to for example make room in the connection
cache and thus that connection is not strictly related to the easy
handle's current operation.

The http authentication state is still kept in the easy handle since all
http auth _except_ NTLM is connection independent and thus survive over
multiple connections.

Bug: http://curl.haxx.se/mail/lib-2014-08/0148.html
Reported-by: Paras S

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.

warning: declaration of 'minor' shadows a global declaration

A conditionally compiled block in connect.c references WinSock 2
symbols, but used `#ifdef HAVE_WINSOCK_H` instead of `#ifdef
HAVE_WINSOCK2_H`.

Bug: http://curl.haxx.se/mail/lib-2014-08/0155.html

The URL is not a property of the connection so it should not be freed in
the connection disconnect but in the Curl_close() that frees the easy
handle.

Bug: http://curl.haxx.se/mail/lib-2014-08/0148.html
Reported-by: Paras S

Should've been amended in the previous commit but wasn't due to a
mistake.

... and some other cleanups

...From "mutual" to "mutual_auth" which better describes what it is.

Corrected a number of the error codes that can be returned from the
Curl_sasl_create_gssapi_security_message() function when things go
wrong.

It makes more sense to return CURLE_BAD_CONTENT_ENCODING when the
inbound security challenge can't be decoded correctly or doesn't
contain the KERB_WRAP_NO_ENCRYPT flag and CURLE_OUT_OF_MEMORY when
EncryptMessage() fails. Unfortunately the previous error code of
CURLE_RECV_ERROR was a copy and paste mistakes on my part and should
have been correct in commit 4b491c67 :(

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.