merge xf86-video-nouveau 1.0.18

various updates to build against xorg-server 21.1.3.

- avoid a const issue with an expanded __UNCONST().
- cope with renamed member names
- deal with "xf86RamDac.h" going away (now use "xf86Cursor.h")

initial import of xf86-video-nouveau-1.0.13

initial import of xf86-video-nouveau-1.0.11