Git commits in Moodle 3.6.3 by Mark Johnson

commit 0c81fe1f2ea7af4a292730e8516fd35888e5b307
Author: Mark Johnson <mark.johnson@open.ac.uk>
Date:   Mon, 18 Feb 2019 22:03:52 +0800
Tag:    v3.6.3

MDL-64889 completion: Fix performance of get_course_progress_percentage