Include the SquirrelMail initialization file.

If a message is viewed from the search page, $aMailbox[$passed_id]['MESSAGE_OBJECT'] is not initialized, which makes this page error out on line 65 with an undefined function. We need to include some additional files in case the object has not been initialized.

TODO: Determine why the object in question is not initialized when coming from a search page and correct. Once that is done, we can remove these includes.