Change drm Map handles to be arbitrary 32-bit hash tokens in the range

Change drm Map handles to be arbitrary 32-bit hash tokens in the range
    0x10000000 to 0x90000000 in PAGE_SIZE increments.
Implement hashed map lookups.
This potentially breaks both 2D and 3D drivers. If so, the corresponding
2D and 3D driver should be fixed, and it's corresponding drm device driver
    should have its major bumped as soon as possible.
Bump sis and via drm device driver majors.
The SiS and Unichrome 3D drivers are fixed in Mesa CVS HEAD and
    mesa_6_4_branch.