Git commits in Moodle 2.6.x by Francis Devine

commit 5536a5617c1c1a0073d8ebe53e08191c5a3b9aac
Author: Francis Devine <francis@xeon.pw>
Date:   Wed, 04 Sep 2013 17:21:41 +0800
Tag:    v2.6.0-beta

MDL-41417 course: prevent duplicate idnumbers being used when updating a course