remove the latest change (it was redundant, as a glsl shader sure can query the textu...

remove the latest change (it was redundant, as a glsl shader sure can query the texture matrix), and instead add an example 6-tap blur filter to the glsl code.

To test:
r_glsl_postprocess 1
r_glsl_postprocess_uservec1 "3 0 0 0"

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@8641 d7cf8633-e32d-0410-b094-e92efae38249