Git merges in Moodle 3.3.x by AMOS bot

commit 4534c7b5315d3a6d427ba6701a1e86ccd367f6a9
Author: AMOS bot <amos@moodle.org>
Date:   Sat, 24 Jun 2017 00:08:53 +0800
Tag:    v3.3.1

Merge branch 'MOODLE_33_STABLE' into install_33_STABLE