Corrected the order of the CAPA / CAPABILITY state machine constants to
match the execution order.

Added honoring of the tls_supported flag when starting a TLS upgrade
rather than unconditionally attempting it. If the use_ssl flag is set
to CURLUSESSL_TRY and the server doesn't support TLS upgrades then the
connection will continue to authenticate. If this flag is set to
CURLUSESSL_ALL then the connection will complete with a failure as it
did previously.

Added honoring of the tls_supported flag when starting a TLS upgrade
rather than unconditionally attempting it. If the use_ssl flag is set
to CURLUSESSL_TRY and the server doesn't support TLS upgrades then the
connection will continue to authenticate. If this flag is set to
CURLUSESSL_ALL then the connection will complete with a failure as it
did previously.

Added honoring of the tls_supported flag when starting a TLS upgrade
rather than unconditionally attempting it. If the use_ssl flag is set
to CURLUSESSL_TRY and the server doesn't support TLS upgrades then the
connection will continue to authenticate. If this flag is set to
CURLUSESSL_ALL then the connection will complete with a failure as it
did previously.

Added sending of initial CAPA command before STLS is sent. This allows
for the detection of the capability before trying to upgrade the
connection.

Added sending of initial CAPABILITY command before STARTTLS is sent.
This allows for the detection of the capability before trying to
upgrade the connection.

Introduced detection of the STARTTLS capability, in order to add support
for TLS upgrades without unconditionally sending the STARTTLS command.

Introduced detection of the STLS capability, in order to add support
for TLS upgrades without unconditionally sending the STLS command.

Introduced detection of the STARTTLS capability, in order to add support
for TLS upgrades without unconditionally sending the STARTTLS command.

Follow up fix to commit 62bd2174 to cater for servers that don't
respond with a 250 in their EHLO responses. Additionally updated the
SMTP tests to respond with a 250 response code as per RFC5321.

Fixed the SASL capability detection to include the space character
before the authentication mechanism list. Otherwise a capability such
as SASLSOMETHING would be interpreted as enabling SASL and potentially
trying to identify SOMETHING as a mechanism.

Corrected an incorrect return value when -ERR is received from the
server - introduced in commit b5bb61ee (June 2012).

Follow up fix to commit 23d17190 as EHLO capabilities can exist
within a positive response line.

Follow up to commit 40f9bb78 to fix missing capabilities after an
AUTH line.

Previously if a problem was found with one of the server's certificates,
we'd log an OSStatus for the end user to look up. Now we explain what
was wrong with the site's certificate chain. Also un-did part of the
previous commit where the code wouldn't catch errSSLServerAuthCompleted
if built under Leopard.

Fixed a small issue where smtp_endofresp() would look for capabilities
in the description part of a failure response. In theory a server
shouldn't respond with SIZE or AUTH in an EHLO command's failure
response but if it did then capabilities would be unnecessarily set
before eventually failing.

Reworked pop3_endofresp() to simplify it and provide consistency between
imap and smtp.

Renamed the authstate1 and authstate2 variables in imap_authenticate()
as the old name was a left over from when there was only one state
variable which was named due to a clash with the state() function.

Additionally this provides consistency with the smtp module.

Renamed the login password response function to better describe it's
purpose as well as for consistency with the imap and pop3 modules.

Running tests\libtest\libntlmconnect.exe reveals a 1 byte (!) leak in
./lib/curl_ntlm_msgs.c:

perl ..\memanalyze.pl c:memdebug.curl
Leak detected: memory still allocated: 1 bytes
At 9771e8, there's 1 bytes.
allocated by curl_ntlm_msgs.c:399

Snippet from curl_ntlm_msgs.c:
   /* setup ntlm identity's domain and length */
   dup_domain.tchar_ptr = malloc(sizeof(TCHAR) * (domlen + 1));

(my domlen == 0).

'dup_domain.tbyte_ptr' looks to be freed in Curl_ntlm_sspi_cleanup() via
'ntlm->identity.Domain'. But I see no freeing of 'dup_domain.tchar_ptr'.

This bug report properly identified that when doing SMTP and aborting
the transfer with a callback, it must be considered aborted prematurely
by the code to avoid QUIT etc to be attempted as that would cause a
hang.

The new test case 1507 verifies this behavior.

Reported by: Patricia Muscalu
Bug: http://curl.haxx.se/bug/view.cgi?id=1184

It turns out that Leopard (OS X 10.5) doesn't have constants for the ECDH
ciphers in its headers, so the cases for them have been taken out of the
build when building under Leopard. Also added a standard function for
getting a string description of a SecCertificateRef.

Modified imap_authenticate() to add support for sending the initial
response with the AUTHENTICATE command, as per RFC4959.

Changed the SMTP_AUTH_PASSWD state constant to SMTP_AUTH_LOGIN_PASSWD to
better describe the state as the second part of an AUTH LOGIN command,
as well as for consistency with the imap and pop3 modules.

Introduced detection of the SASL-IR capability, in order to add support
for sending the initial response with the AUTHENTICATE command, as per
RFC4959.

This reverts commit 0e66d587.

Updated the automatic response tag generation to follow the examples
given in RC3501, which list a 4 character string such as A001, A002,
etc.

As a unique identifier should be generated for each command the string
generation is based on the connection id and the incrementing command
id.

This is untested, but ought to be enough to still allow it
to work automatically when the entire curl source tree is
dropped into a full Android source tree.

VC6 is _very_ old and we provide working makefiles even for that
compiler. Users who build with the IDE never use that method and project
file anyway and it was just lingering in the root dir.

Renamed a couple of variables and updated some comments in
preparation for upcoming command id / response tag change.