Author: Petr Škoda
MDL-39846 implement new event dispatching and base event class
http://git.moodle.org/gw?p=moodle.git;a=commit;h=d8a1f4263a3f18822ab53aeaded1e684aed94213
http://github.com/moodle/moodle/commit/d8a1f4263a3f18822ab53aeaded1e684aed94213
+ 2.6 en [cachedef_observers,core_cache]