- Y tiling support for scanout from Tvrtko&Damien

- Remove more UMS support
- some small prep patches for OLR removal from John Harrison
- first few patches for dynamic pagetable allocation from Ben Widawsky, rebased
  by tons of other people
- DRRS support patches (Sonika&Vandana)
- fbc patches from Paulo
- make sure our vblank callbacks aren't called when the pipes are off
- various patches all over