Author: David Monllao
MDL-48838 grades: New grade_categories cache
http://git.moodle.org/gw?p=moodle.git;a=commit;h=28774c9263fd913ee691d153d77e27ef77fdd729
http://github.com/moodle/moodle/commit/28774c9263fd913ee691d153d77e27ef77fdd729
+ 3.1 en [cachedef_grade_categories,core_cache]