Author: Marcus Boon
MDL-79930 mod_forum: Use MUC for forum count discussions
http://git.moodle.org/gw?p=moodle.git;a=commit;h=8f4d6f460d90e714fe00f5573c4784d57a1c893d
http://github.com/moodle/moodle/commit/8f4d6f460d90e714fe00f5573c4784d57a1c893d
+ 4.2 en [cachedef_forum_count_discussions,mod_forum]