send-email --smtp-server-port: allow overriding the default port

You can use --smtp-server-port option to specify a port
different from the default (typically, SMTP servers listen
to smtp port 25 and ssmtp port 465).

Users should be aware that sending auth info over non-ssl
connections may be unsafe or just may not work at all
depending on SMTP server config.

Signed-off-by: Glenn Rempe <glenn@rempe.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-send-email.txt

@@ -91,6 +91,11 @@ The --cc option must be repeated for each user you want on the cc list.
 	`/usr/lib/sendmail` if such program is available, or
 	`localhost` otherwise.
 
+--smtp-server-port::
+	Specifies a port different from the default port (SMTP
+	servers typically listen to smtp port 25 and ssmtp port
+	465).
+
 --smtp-user, --smtp-pass::
 	Username and password for SMTP-AUTH. Defaults are the values of
 	the configuration values 'sendemail.smtpuser' and