Git commits in Moodle 2.9.3 by Jean-Philippe Gaudreau

commit e6b37361a1b60717fe1a22b9640a2f7d798717bd
Author: Jean-Philippe Gaudreau <jp.gaudreau@umontreal.ca>
Date:   Tue, 25 Aug 2015 05:05:44 +0800
Tag:    v2.9.3

MDL-51191 assign: Optimizing slow SQL query for MySQL