winhlp32: Make use of the hlpfile for the running macro to handle correctly some macro implementations.

Enabling the NV extensions occupies a temp register for some reason. Avoid
needlessly enabling it.

Otherwise the Nvidia assembler needs one temp reg.

This reverts patch ba35760f.

The original patch did not achive its goal, because CMP is a macro that is
expanded to SLT, SGE, MUL, MAD, at least on nvidia hardware. To make matters
worse, it uses a temporary register, and the assembler usually is not clever
enough to find a free temporary from the shader code. If we generate the code
outselves we can pick one of our temps for this job.

This removes another reason to declare TA, TB and TC.