Author: Petr Skoda
MDL-28273 waring that removing user from cohorts may unenrol from courses
http://git.moodle.org/gw?p=moodle.git;a=commit;h=c43a4beda87fa491293d8e477b666afa6fbeb487
http://github.com/moodle/moodle/commit/c43a4beda87fa491293d8e477b666afa6fbeb487
+ 2.1 en [removeuserwarning,core_cohort]