* Various changes to begin work on support for MIME messages

    * Various changes to begin work on support for MIME messages
                - Defined format type 4 for MIME
                - msgbase.c: *temporary* hacks in output_message() for Type 4
                - citmail.c: added more robust header parsing, and support
                             for Type 4.  Also eliminated the crappy built-in
                             SMTP server.
                - Updated some of the technical documentation