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.

If you are going to test an enum value for equality with -1,
and -1 is out of range for the enum type,
then at least cast the -1 to the appropriate enum type.

initial import of xf86-video-nv-2.1.18

initial import of xf86-video-nv-2.1.17

initial import of xf86-video-nv-2.1.14

initial import of xf86-video-nv-2.1.13

initial import of xf86-video-nv-2.1.10