* Implement RasterizeEnable
* Match viewport count to hardware
* Simplify ScissorTest tracking around Blits
* Disable RasterizerDiscard around Blits and track its state
* Read RasterizeEnable reg as bool and add doc
Support shared color masks (used by Nouveau and maybe the NVIDIA
driver).
Support draw buffers (also required by OpenGL).
Support viewport transform disable (disabled for now as it breaks some
games).
Fix instanced rendering draw being ignored for multi draw.
Fix IADD and IADD3 immediate shader encodings, that was not matching
some ops.
Implement FFMA32I shader instruction.
Implement IMAD shader instruction.
