tests: Added POP3 DIGEST-MD5 authentication test
sasl: fix compiler warning

error: unused variable 'table16'
tests: Added empty response support to custom replies

...and fixed up test869 as DIGEST-MD transcript is as follows:

S: Challenge
C: Authentication String
S: Continue Response
C: Empty String
tests: Added POP3 OAUTH2 authentication test
CURLOPT_RESOLVE: mention they don't time-out

Clarify in the documentation that DNS entries added with CURLOPT_RESOLVE
won't time-out.

Bug: http://curl.haxx.se/mail/lib-2013-10/0062.html
Reported-by: Romulo Ceccon
ftpserver.pl: Added support for empty pop3 authentication data
sasl: Fixed memory leak in OAUTH2 message creation
OS400: sync RPG wrapper, zlib support, fix header file names, ...
IFS compilation support, SSL GSKit backend by default, TLSv1.[12] support in
  GSKit for OS400 >= V7R1, no more tabs in make scripts.
tests: Regrouped SMTP authentication tests
tests: Added SMTP DIGEST-MD5 authentication test
tests: Added SMTP OAUTH2 authentication test
tests: Added SMTP NTLM authentication with initial response test
tests: Added SMTP OAUTH2 authentication with initial response test
RELEASE-NOTES: Synced with d24b7953c2132a
test907: Corrected DIGEST-MD5 response given in commit 820ed48a0088cd

As the URI, which is contained within the DIGEST-MD5 response, is
constructed from the service and realm, the encoded message differs
from that generated under POP3.
gskit.c: Code policing following commit 2cc9246477285d

Corrected 80 character line length error and pointer declarations (some
of which were previously incorrect)
smtp: Fixed response code parsing for bad AUTH continuation responses

This workaround had been previously been implemented for IMAP and POP3
but not SMTP. Some of the recent test case additions implemented this
behaviour to emulate a bad server and the SMTP code didn't cope with it.
tool_help: Added clarity to the --oauth2-bearer option

...as XOAUTH2 is the extended (or non-standard) SASL identifier and
OAuth 2 is the protocol name (and version).
tests: Tidy up of SMTP and POP3 tests

Corrected line endings, RFC references and standardised on user names
and passwords used in the tests.
email: Added references to SASL LOGIN authentication draft proposal