* On 32 bit platforms we steal the upper 4 bits of the map handle
to store a unique map id.
* On 64 bit platforms we steal the upper 24 bits.
Resolves issues where the offsets that are handed to mmap may overlap the VRAM on some cards.
Tested on: radeon, intel, mga, and via.
This will break nouveau. I will spin new patches shortly.
- Don't bother to assign vb until we know we have enough space
- Add variables for sx2, sy2, dx2, dy2 so that these aren't
calculated over and over, also reduce chance of errors.
- Use switch to assign color/format
MFC after: 3 days
