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.

... to handle "*/[total]". Also, removed the strange hack that made
CURLOPT_FAILONERROR on a 416 response after a *RESUME_FROM return
CURLE_OK.

Reported-by: Dimitrios Siganos
Bug: http://curl.haxx.se/mail/lib-2014-06/0221.html

warning: unused variable 'resp'

warning: no previous prototype for 'Curl_sasl_gssapi_cleanup'

* curl_sasl_sspi.c: Fixed compilation warning from commit 4b491c67

warning: declaration of 'result' shadows a previous local

warning: 'struct kerberos5data' declared inside parameter list

Due to missing forward declaration.

warning: extra tokens at end of #endif directive

Added a kerberos5data structure which is similar in nature to the
ntlmdata and negotiatedata structures.

In preparation for the upcoming SSPI implementation of GSSAPI
authentication, moved the definition of KERB_WRAP_NO_ENCRYPT from
socks_sspi.c to curl_sspi.h allowing it to be shared amongst other
SSPI based code.

... as mxr.mozilla.org is due to be retired.

The new host doesn't support If-Modified-Since nor ETags, meaning that
the script will now defer to download and do a post-transfer checksum
check to see if a new output is to be generated. The new output format
will hold the SHA1 checksum of the source file for that purpose.

We call this version 1.22

Reported-by: Ed Morley
Bug: http://curl.haxx.se/bug/view.cgi?id=1409