Git merges in Moodle 3.1.16 by David Monllao

commit 786fe599494740156bfa13be4c3e40e137ccb423
Author: David Monllao <davidm@moodle.com>
Date:   Tue, 20 Nov 2018 19:55:04 +0800
Tag:    v3.1.16

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