Replace all legacy events related to cohort.
cohort/lib.php: events_trigger('cohort_added', $cohort);
cohort/lib.php: events_trigger('cohort_updated', $cohort);
cohort/lib.php: events_trigger('cohort_deleted', $cohort);
cohort/lib.php: events_trigger('cohort_member_added', (object)array('cohortid'=>$cohortid, 'userid'=>$userid));
cohort/lib.php: events_trigger('cohort_member_removed', (object)array('cohortid'=>$cohortid, 'userid'=>$userid));