Author: Mark Nelson
MDL-54687 core_message: added ability to delete messages
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3090f52f9d8794deb9820f424c05326bfaea9d1c
http://github.com/moodle/moodle/commit/3090f52f9d8794deb9820f424c05326bfaea9d1c
+ 3.2 en [selectmessagestodelete,core_message]