nak: try and fix a few nak things.
- compute headless test crashes due to encoding error
- fragment shader INTERP_NONE should do perspective
- the IPA fields are encoded different than nvc0
- the latency calculator
- crashes when setting interp for position
4 is a hacky best effort, but it does fix things so that fragment shaders render triangle, gears, textures from the Sascha demos.
Edited by Dave Airlie