Git commits in Moodle 2.3.7 by Mike Churchward

commit 54f03faba2543502c82d5a8aa1a248d391f1869d
Author: Mike Churchward <mike@remote-learner.net>
Date:   Wed, 17 Apr 2013 22:18:55 +0800
Tag:    v2.3.7

MDL-34933 core_message: Adding index to improve database access on message_working table.