Comment # 9 on bug 66384 from Michel Dänzer

Fixed in xf86-video-ati Git master:

commit 0288a4b87b65ba54f37fbeeea3cb32238deee92e
Author: Michel Dänzer <michel.daenzer@amd.com>
Date:   Wed Aug 19 16:54:14 2015 +0900

    DRI2: Keep MSC monotonic when moving window between CRTCs