Author: Ryan Wyllie
MDL-63303 message: add enter to send user preference
http://git.moodle.org/gw?p=moodle.git;a=commit;h=8c8939c1ae7f68deba2855ec9e15cf8ac9967b1b
http://github.com/moodle/moodle/commit/8c8939c1ae7f68deba2855ec9e15cf8ac9967b1b
+ 3.6 en [useentertosend,core_message]