Git commits in Moodle 2.8.9 by Pau Ferrer Ocaña

commit 3262330d95971fc966b59f4647f37d6b7991c2ec
Author: Pau Ferrer Ocaña <crazyserver@gmail.com>
Date:   Wed, 23 Sep 2015 23:02:39 +0800
Tag:    v2.8.9

MDL-50805 Messages: Add index to message_read to speed up message crons