Author: David Woloszyn
MDL-82944 message: Notify user about unsent messages
http://git.moodle.org/gw?p=moodle.git;a=commit;h=1afbe03ec8e8eeffb158ac30fa2a36cebe06c9a2
http://github.com/moodle/moodle/commit/1afbe03ec8e8eeffb158ac30fa2a36cebe06c9a2
+ 5.0 en [unsentmessagenotification,core_message]