2.5.0. It still has some issues, including a flicker in the fps meter
in tuxracer and I've seen garbage left behind after moving/closing
windows. However, it's usable. Add the Option "EnablePageFlip" "YES" to
use it.
DRM_*MEMORYBARRIER we had were related to an MMIO space. This means
arch-specific code on the BSDs, unfortunately. Also add
DRM_MEMORYBARRIER() and change the DRM_READMEMORYBARRIER()s that used
to be read/write barriers to it.