Author: Mark Nelson
MDL-40913 core_message: replaced 'remove contact' add_to_log call with an event
http://git.moodle.org/gw?p=moodle.git;a=commit;h=5edf9f3bd3bcca1e490dcc7535638182a09637ad
http://github.com/moodle/moodle/commit/5edf9f3bd3bcca1e490dcc7535638182a09637ad
+ 2.7 en [eventmessagecontactremoved,core_message]