Fix forwarding from the Mailbox list. I posted to the Devel list about this on June...

Fix forwarding from the Mailbox list.  I posted to the Devel list about this on June 6, but got no response.  We need to forward to the compose page, but instead it forwards back to itself ($PHP_SELF) which just makes it refresh the page.  I am working on fixing one last issue with it now.  When forwarding, unread messages appear to be marked as read in the cache, even when they aren't in message list (refreshing both frames still leaves them out of synch).

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@7941 7612ce4b-ef26-0410-bec9-ea0150e637f0