smtp: Fixed an issue with missing capabilities after the AUTH line

Follow up to commit 40f9bb787f05 to fix missing capabilities after an
AUTH line.
smtp: Fixed an issue when processing EHLO failure responses (Part 2)

Follow up fix to commit 23d17190ee32 as EHLO capabilities can exist
within a positive response line.
pop3: Fixed incorrect return value from pop3_endofresp()

Corrected an incorrect return value when -ERR is received from the
server - introduced in commit b5bb61ee697b (June 2012).
pop3: Fixed SASL authentication capability detection

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.
smtp: Fixed an issue when processing EHLO failure responses (Part 3)

Follow up fix to commit 62bd21746443 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.
Merge remote-tracking branch 'bagder/master'
RELEASE-NOTES: synced with 92f7606f29b704
imap: Added support for the STARTTLS capability (Part One)

Introduced detection of the STARTTLS capability, in order to add support
for TLS upgrades without unconditionally sending the STARTTLS command.
pop3: Added support for the STLS capability (Part One)

Introduced detection of the STLS capability, in order to add support
for TLS upgrades without unconditionally sending the STLS command.
smtp: Added support for the STLS capability (Part One)

Introduced detection of the STARTTLS capability, in order to add support
for TLS upgrades without unconditionally sending the STARTTLS command.
imap: Added support for the STARTTLS capability (Part Two)

Added sending of initial CAPABILITY command before STARTTLS is sent.
This allows for the detection of the capability before trying to
upgrade the connection.
pop3: Added support for the STLS capability (Part Two)

Added sending of initial CAPA command before STLS is sent. This allows
for the detection of the capability before trying to upgrade the
connection.
htmltitle: fix suggested build command
imap: Added support for the STARTTLS capability (Part Three)

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.
pop3: Added support for the STLS capability (Part Three)

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.
smtp: Added support for the STARTTLS capability (Part Two)

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.
imap: Fixed memory leak following commit f6010d9a0359
email: Post STARTLS capability code tidy up (Part One)

Corrected the order of the CAPA / CAPABILITY state machine constants to
match the execution order.
Fix NULL pointer reference when closing an unused multi handle.
RELEASE-NOTES: Updated following the recent imap/pop3/smtp changes