Changed: Improve the fatal error shutdown handler. Wrap Exception Handler in try catch to trap exceptions thrown in the handler itself.
Changed: Normalised PM database structure to allow storing single message with multiple recipients without duplication of data.
Changed: Email post to, thread and folder subscriptions notifications now use queries and not the other functions to get results.
Changed: Allow multiple recipients in posts.
Changed: Remove check_install and don't call it in boot.php.
Changed: Refined installer to remove duplicate HTML output and specify required includes.
Changed: Installer should now work for PHP 5.2.x.