some cleanup of the GLSL shader, no longer uses #ifdef variable declarations because...

some cleanup of the GLSL shader, no longer uses #ifdef variable declarations because the shader compiler removes unused variables anyway, and now always calculates the eye vector for simplicity reasons
removed the SURFACENORMALIZE option (now always on, since it doesn't cost much render time and was on by default)
removed all use and detection of half floats (these were originally around 11% speedup on GF6 hardware but but in more recent drivers they've dropped to around 3-6%, and spit out a lot of warnings during shader compilation with no apparent way to fix the warnings)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@6228 d7cf8633-e32d-0410-b094-e92efae38249