Git merges in Moodle 3.1.9 by David Monllao

commit fab3e4fa3df6c28f8c57068ca32eea17802164b8
Author: David Monllao <davidm@moodle.com>
Date:   Fri, 27 Oct 2017 18:48:22 +0800
Tag:    v3.1.9

Merge branch 'install_31_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_31_STABLE