Get libnotify notifications working without dependencies

[abi]

Firefox 3.6 (the release is still quite some time away) has support for this but we should probably support to it on 3.5 too. It should be easy to do with a C XPCOM module. See http://manishtech.wordpress.com/2009/03/29/working-with-libnotify/ and http://getsatisfaction.com/mozilla/topics/support_libnotify_based_notifications_on_linux