merge xf86-video-mach64 6.9.4, xf86-video-mga 1.6.2, xf86-video-nv 2.1.20,
and xf86-video-r128 6.9.1.

When checking for an unimplemented MMIO BAR also check for an uninitialized one
This allows the mach64 driver to work on a PowerMac G3, the firmware here
leaves 0xfffff000 in the MMIO BAR.

initial import of xf86-video-mach64-6.8.0