Author: Charles Fulton
MDL-64528 core_completion: prevent toggling completion in frozen context
http://git.moodle.org/gw?p=moodle.git;a=commit;h=f7afadd846f7a6b15f736b05220c8878a18a0c06
http://github.com/moodle/moodle/commit/f7afadd846f7a6b15f736b05220c8878a18a0c06
+ 3.6 en [course:togglecompletion,core_role]