Git merges in Moodle 3.1.16 by Jun Pataleta

commit 53c902867f695c1da339d063eb9a2e9aab2f0364
Author: Jun Pataleta <jun@moodle.com>
Date:   Mon, 19 Nov 2018 15:45:03 +0800
Tag:    v3.1.16

Merge branch 'MDL-63994-31-castoken' of git://github.com/mudrd8mz/moodle into MOODLE_31_STABLE