Author: Ryan Wyllie
MDL-66144 course: add function to calculate user course dates
http://git.moodle.org/gw?p=moodle.git;a=commit;h=00a66396c71b7241e04371bf70254b95c73047dc
http://github.com/moodle/moodle/commit/00a66396c71b7241e04371bf70254b95c73047dc
+ 3.8 en [cachedef_course_user_dates,core_cache]