Git merges in Moodle 3.1.9 by Andrew Nicols

commit 853fbda447469ed61d9c6ad9b455ecbb41b4d3a8
Author: Andrew Nicols <andrew@nicols.co.uk>
Date:   Thu, 26 Oct 2017 14:35:45 +0800
Tag:    v3.1.9

Merge branch 'wip-MDL-60543-31' of git://github.com/marinaglancy/moodle into MOODLE_31_STABLE