Git commits in Moodle 2.5.6 by Tony Levi

commit 889603945ca9c5dba11cdb2c507d6026a19679e5
Author: Tony Levi <tony.levi@netspot.com.au>
Date:   Wed, 02 Apr 2014 11:30:19 +0800
Tag:    v2.5.6

MDL-44908: Fix upgrade_grade_item_fix_sortorder performance