Author: Andrew Nicols
MDL-62079 core_filters: Implement null provider
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3fd4a77fde187f1e4cf45925d1c4f6f22c08325c
http://github.com/moodle/moodle/commit/3fd4a77fde187f1e4cf45925d1c4f6f22c08325c
+ 3.4 en [privacy:reason,core_filters]