Git commits in Moodle 3.3.6 by Marcus Fabriczy

commit a83ceb2be84f6ff97ed819678a8be53e3a1c0034
Author: Marcus Fabriczy <marcus.fabriczy@blackboard.com>
Date:   Tue, 03 Apr 2018 11:14:16 +0800
Tag:    v3.3.6

MDL-60196 core_course: Fix the display of custom LTI icons