add error checking to the GL_ATI_FRAGMENT_SHADER entrypoints. Fix bug with scope...

add error checking to the GL_ATI_FRAGMENT_SHADER entrypoints. Fix bug with scope of ati fragment shader constants. Fix issues with specifying color/alpha instructions not pair-wise. Change internal representation of the shader (to better fit how the extension works, should make driver implementations simpler, and saves some memory). (still doesn't work correctly with doom3 and swrast, but not worse than before)