There is no point in having SSL/TLS IMAP support as optional, it's as
useful if not more than the the non-encrypted connections.
The Makefile was better organized to make it easier to change some
options during compile.
The SHAREDIR variable passed as configuration option has changed name.
Move the source code to the src dir, the man pages to the doc dir, and
the example configuration files to the samples dir, and update all
relevant files to reflect the changes.
