comparison between signed and unsigned integer expressions

If the mail sent during the transfer contains a terminating <CRLF> then
we should not send the first <CRLF> of the EOB as specified in RFC-5321.

Additionally don't send the <CRLF> if there is "no mail data" as the
DATA command already includes it.

... which was missed in commit: f5c3d953

... which was missed in commit: f5c3d953

Introduced in commit: 51481766

...and removed references to libcurl and test1406.

The code within #ifdef HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID wrongly had two
closing braces when it should only have one, so builds without that
define would fail.

Bug: http://curl.haxx.se/mail/lib-2013-05/0000.html

Move the eob counter from the smtp_conn structure to the SMTP structure
as it is associated with a SMTP payload on a per-request basis.

The curl command line utility would display the the completed progress
bar with a percentage of zero as the progress routines didn't know the
size of the transfer.

Fix regressions in commit b56e3d43. Make @data local and filter off
non-numerical digits from $testno in STATUS_imap.

...to be more realistic and consistent with the other imap responses.

The emails that are sent to the server during these tests were
incorrectly formatted as they contained one or more LF terminated lines
rather than being CRLF terminated as per Section 2.3.7 of RFC-2821.

This wasn't a problem for the test suite as the <stdin> data matched the
<upload> data but anyone using these tests as reference would be sending
incorrect data to a server.

Removed the hard returns from imap and pop3 by using the same style for
sending the authentication string as smtp. Moved the "Other mechanisms
not supported" check in smtp to match that of imap and pop3 to provide
consistency between the three email protocols.

Added 255 octet limit check as per Section 4. Paragraph 8 of RFC-5034.

Users using the Secure Transport (darwinssl) back-end can now use a
certificate and private key to authenticate with a site using TLS. Because
Apple's security system is based around the keychain and does not have any
non-public function to create a SecIdentityRef data structure from data
loaded outside of the Keychain, the certificate and private key have to be
loaded into the Keychain first (using the certtool command line tool or
the Security framework's C API) before we can find it and use it.

Since we're adding new stuff, the next release will bump the minor
version and we're looking forward to 7.31.0

Documented the the option in curl_easy_setopt() and added it to
symbols-in-versions.

Updated test903 and test904 following the addition of CURLOPT_SASL_IR
as the default behaviour of SMTP AUTH responses is now to not include
the initial response. New tests with --sasl-ir support to follow.

In addition to checking for the SASL-IR capability the user can override
the sending of the client's initial response in the AUTHENTICATION
command with the use of CURLOPT_SASL_IR should the server erroneously
not report SASL-IR when it does support it.

Updated the default behaviour of sending the client's initial response in the AUTH
command to not send it and added support for CURLOPT_SASL_IR to allow the user to
specify including the response.

Related Bug: http://curl.haxx.se/mail/lib-2012-03/0114.html
Reported-by: Gokhan Sengun

Allowed the user to specify whether to send the client's intial response
in the AUTH command via CURLOPT_SASL_IR.