default_mail{_in|_out}_directory() methods in the BPrivate namespace.
* Used these methods in the inbound/outbound protocols.
* Moved WriteMessageFile() into the BPrivate namespace as well, and put its
prototype into a new header MailPrivate.h along with the new directory
getters.
* Removed the automatic copy to the sent directory again, and only have one
directory for incoming mail. Incidentally, this fixed#7509, although the
underlying filter restriction remains.
* Automatic whitespace cleanups, some style cleanups. Sorry for the mess.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42260 a95241bf-73f2-0310-859d-f6bbb57e9c96
