PixelShaderGen: Simplify tev code by dropping some optimizations (shader compilers do this automatically, anyway).
PixelShaderGen: Simplify tev compare code.
PixelShaderGen: Simplify tev code by introducing some local variables.
PixelShaderGen: Simplify clamping code.
PixelShaderGen: Always check for U8 overflow in tev stage combiners.
PixelShaderGen: Remove old overflow emulation code.
PixelShaderGen: Fix alpha compare (relying on accurate tev register bitness emulation and precise GPU calculations).
PixelShaderGen: Fix tev compare (relying on accurate tev register bitness emulation and precise GPU calculations).
PixelShaderGen: Always clamp tev stage output at least to S11 range.
PixelShaderGen: Add helper macros to vastly clean up overflow+precision emulation.

Also fixed some bitness emulation bugs.
PixelShaderGen: Fix a small issue in the comp16/24 stuff. 1.0f*1.0f equals (1/255.0f)*255.0f!
PixelShaderGen: Emulate limited resolution of RGBA6 and RGB565 EFB formats.
PixelShaderGen: Cleanup some tev code.
PixelShaderGen: Declare variables as late as possible (or not at all if it's not necessary).
PixelShaderGen: Optimize tev stage combiner input loading.
PixelShaderGen: Use correct values for constants other than one and zero.
PixelShaderGen: Fix alphabump value not being of the correct precision.
Move some tables to wherever they're used.
PixelShaderGen: Cleanup SampleTexture calls.
PixelShaderGen: Cleanups.
PixelShaderGen: I don't see why this would need to be 0.001f instead of 0.0f.