Fragment Program improvements and additions

+ Added TODOs for REFL, LIT, LRP, BEM, TEXBEM and TXPBEM
- Removed the warning message about TEX_SRB texture projection being
used
* Implemented packSnorm2x16, unpackSnorm2x16, packSnorm4x8 and
unpackSnorm4x8. All need more testing to be confirmed as working
Merge pull request #936 from tambry/FPImprovements

Fragment Program improvements and additions