Author: Mark Nelson
MDL-63466 core_message: rename cache for last message time
http://git.moodle.org/gw?p=moodle.git;a=commit;h=f978593d6c3b98db5b3feb29448a642b4f540edc
http://github.com/moodle/moodle/commit/f978593d6c3b98db5b3feb29448a642b4f540edc
+ 3.6 en [cachedef_message_time_last_message_in_conversation,core_cache]
- 3.6 en [cachedef_message_time_last_message_between_users,core_cache]