Support predicates.

Support predicates.

Predicates, as per D3D9 spec, are a complete subset of NVIDIA's
condition codes. However, due to its broad support in non-NVIDIA
hardware, it is being exposed in TGSI to ease hw driver development.
Two decomposition functions are expected in the future.
1. GetRidOfPredicates() - predicates are implemented with condition
codes.
2. There is no second function, it's just this pesky VI that does not
allow me to move with arrow keys and so I cannot edit previous paragraphs.