Comment # 3 on bug 53130 from Darren Salt

I've rebuilt mesa with this re-enabled and I saw a lot of rendering glitches. I
suspect that DISCARD_RANGE being re-enabled is the problem, although I've also
built and installed an updated xf86-video-ati (cdf522f→20bfc65).

My current mesa build has 1eedebc reverted; I'll re-check with that undone
later.