Author: Simey Lameze
MDL-56223 calendar: skip events updating if nothing has changed
http://git.moodle.org/gw?p=moodle.git;a=commit;h=d5727ed3bab91ba295390bed00be8aa10f5c8ac2
http://github.com/moodle/moodle/commit/d5727ed3bab91ba295390bed00be8aa10f5c8ac2
+ 3.8 en [eventsskipped,core_calendar]