help with ati, and future DRM drivers.
- Add new "ati" kdrive driver. It has ancestry in the r128 driver from
    andersca, but took a detour through being the WIP SiS 300 driver on the
    way. It supports Radeons (tested on QD VIVO and 7500) and Rage 128.
    Current limitations include that it requires depth 16 and that the
    other Rage 128 PCI IDs aren't included yet.