Author: Mark Nelson
MDL-64773 core_message: add ability to mute/unmute conversations
http://git.moodle.org/gw?p=moodle.git;a=commit;h=bd038cc19fb9c24c9c45c35878efb849f07c5523
http://github.com/moodle/moodle/commit/bd038cc19fb9c24c9c45c35878efb849f07c5523
+ 3.7 en [muteconversation,core_message]
+ 3.7 en [unmuteconversation,core_message]