Git commits in Moodle 2.7.18 by Dan Poltawski

commit 1504e9b81e67fb4ec85aff58e448a9e155b73dc1
Author: Dan Poltawski <dan@moodle.com>
Date:   Tue, 29 Nov 2016 21:36:11 +0800
Tag:    v2.7.18

weekly release 2.7.17+