[Nouveau] [Patches] mesa/nv30: Diverse set of patches that improve NV3x render quality V2

[Roy Spliet]

A reworked version of 3 out of 4 patches mentioned earlier.

[1/4]: Fixes nearly all piglit vertprog testcases, due to now being able to pass the results on to the fragment shader. V2: rename samplers to texcoords.
[2/4]: Fixes shader compiler assertion errors, as some source registers do not exist for certain operations. Fixes several piglit tests when mesa is compiled with --enable-debug
[3/4]: unchanged
[4/4]: Dropped, requires a more substantial fix. As a quick-fix it's still useable though.

Testers welcome!