Rewrote MIME support and made it much, MUCH quicker. All parsing of the

Rewrote MIME support and made it much, MUCH quicker.  All parsing of the
messages are now handled on the IMAP server, rather than inside PHP, which
makes it about 20x faster (literally).

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@551 7612ce4b-ef26-0410-bec9-ea0150e637f0