Author: Mark Nelson
MDL-40913 core_message: replaced 'write' add_to_log call with an event
http://git.moodle.org/gw?p=moodle.git;a=commit;h=ab1bc5d222320758653692d011ae23d6ccc53f53
http://github.com/moodle/moodle/commit/ab1bc5d222320758653692d011ae23d6ccc53f53
+ 2.7 en [eventmessagesent,core_message]