Overhauled quake3 shader loading such that it now produces shader passes that could...

Overhauled quake3 shader loading such that it now produces shader passes that could render the material mostly correctly (rendering not yet implemented for the pre/post passes the logic identifies).

Main visible effect of this is that quake3 maps look more correct, but don't have any fancy effects yet.

This changed the loaders for all other formats that produce texture_t as texture->materialshaderpass-> is the new source of truth for several things.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12285 d7cf8633-e32d-0410-b094-e92efae38249