Fixed an issue where (lib)curl is compiled without support for a
supported challenge-response based SASL authentication mechanism, such
as CRAM-MD5 or NTLM, the server doesn't support the LOGIN or PLAIN
mechanisms and (lib)curl doesn't fallback to APOP or Clear Text
authentication.

Bug: http://curl.haxx.se/mail/lib-2013-02/0004.html
Reported by: Stanislav Ivochkin

Remove timeout argument that's never used.

Make the actual connection get detected on a single spot to reduce code
duplication.

Store the IPv6 state already when the connection is attempted.

Curl_perfom is no longer used anywhere since the always-multi commit
c4312741, and some related functions were used only from within
Curl_perfom.

- Fix a pair of single quotes to double quotes.

URL: http://curl.haxx.se/mail/lib-2013-01/0355.html
Reported by: Tor Arntsen

- Take into account that 'wc' may return leading spaces and/or tabs.

- Set initial IFS to space, tab and newline.

- Take into account that 'wc' may return leading spaces.

- Set internationalization behavior variables.

Tor Arntsen analyzed and reported the issue.

URL: http://curl.haxx.se/mail/lib-2013-01/0351.html

Added CURLOPT_FOLLOWLOCATION since example.com is now redirected.

There was a bug where, if SSLWrite() returned errSSLWouldBlock but did
succeed in transmitting at least something, then we'd incorrectly
resend the packet. Now we never take errSSLWouldBlock as a sign that
nothing was transferred to/from the server.

Bug: http://curl.haxx.se/mail/lib-2013-01/0295.html
Reported by: Bruno de Carvalho

Even though he's a fine dude, once is enough for this time!

- Stabilization results in 4 public interface m4 macros:
  XC_CONFIGURE_PREAMBLE
  XC_CONFIGURE_PREAMBLE_VER_MAJOR
  XC_CONFIGURE_PREAMBLE_VER_MINOR
  XC_CHECK_PATH_SEPARATOR
- Avoid one level of internal indirection
- Update comments
- Drop XC_OVR_ZZ40 macro

Reported by: Jiri Jaburek
Bug: https://bugzilla.redhat.com/896544

Bug: https://bugzilla.redhat.com/696783

Added CURLOPT_FOLLOWLOCATION since example.com is now redirected.

The state machine should only be changed to SMTP_STARTTLS when the
STARTTLS command has been successfully sent to the server.

The state machine should only be changed to POP3_STARTTLS when the
STLS command has been successfully sent to the server.

The state machine should only be changed to IMAP_STARTTLS when the
STARTTLS command has been successfully sent to the server.

Updated the ssldone comment as multi mode is always used internally now.

This avoids witness message in output when running configure --help,
while sending the message to config.log for other configure runs.

Minor code tidy up to add comments similar to those used in the pop3
and imap end of resp functions, in order to assist anyone reading the
code and highlight the similarities between each of these protocols.

- version conditional overriding
- catch unexpanded XC macros
- fix double words in comments

Tor Arntsen analyzed and reported the issue.

URL: http://curl.haxx.se/mail/lib-2013-01/0306.html

m4 quadrigraph shell comment technique allows proper autoconf
parentheses balancing in shell 'case' statements. The presence
of unbalanced parentheses may otherwise trigger expansion bugs.

The most recent version of the SMTP RFC is RFC5321 and not RFC2821 as
previously documented.

Added RFC1870 and re-ordered list numerically.

smtp_state_upgrade_tls() would attempt to incorrectly complete the
upgrade to smtps and start the EHLO command if
Curl_ssl_connect_nonblocking() returned a failure code and if ssldone
was set to TRUE. This would only happen when a non-blocking API hadn't
been provided by the SSL implementation and curlssl_connect() was
called underneath.

pop3_state_upgrade_tls() would attempt to incorrectly complete the
upgrade to pop3s and start the CAPA command if
Curl_ssl_connect_nonblocking() returned a failure code and if ssldone
was set to TRUE. This would only happen when a non-blocking API hadn't
been provided by the SSL implementation and curlssl_connect() was
called underneath.

imap_state_upgrade_tls() would attempt to incorrectly complete the
upgrade to imaps and start the CAPABILITY command if
Curl_ssl_connect_nonblocking() returned a failure code and if ssldone
was set to TRUE. This would only happen when a non-blocking API hadn't
been provided by the SSL implementation and curlssl_connect() was
called underneath.

- Update comments
- Execute commands in subshells
- Faster path separator check
- Fix missing 'test' command
- Rename private macros
- Minimize AC_REQUIRE usage

Small tidy up to remove unnecessary return statements prior to the next
fix.

Some basic checks we make were placed early enough in generated
configure script when using autoconf 2.5X versions. Newer autoconf
versions expand these checks much further into the configure script,
rendering them useless. Using XC_CONFIGURE_PREAMBLE fixes placement
of early intended checks across all our autoconf supported versions.