On X init, PFIFO and PGRAPH are reset to defaults. This causes the GPU to
loose the configuration done by the drm. Perhaps a CARD_INIT ioctl a proper
solution to having this problem again in the future..
Added preliminary support for context switches (triggers the interrupts, but hangs after the switch ; something's not quite right yet).
Removed the PFIFO_REINIT ioctl. I hope it's that a good idea...
Requires the upcoming commit to the DDX.