Git commits in Moodle 3.1.5 by Daniel Thee Roperto

commit 33952ce027e59c1c0913cb1a4cbb73d2dee9d1e0
Author: Daniel Thee Roperto <danielroperto@catalyst-au.net>
Date:   Thu, 05 Jan 2017 12:31:31 +0800
Tag:    v3.1.5

MDL-57576 assignment: Overwrite feedback file if it has the same name.