Fix most Q3 & QL glow maps

Fix most Q3 & QL glow maps

From bones_was_here: "Very few glow maps work in unmodified Q3 maps as they do not use the _glow darkplaces convention, instead Q3 shaders specify the file name to use which is not currently supported.
Fortunately there is a naming convention started in id software's pak0 and continued in QL and most 3rd party maps.  It uses these forms: foo_texture.blend.ext and bar_texture_blend.ext
It's not possible to fix 100% of glow maps without parsing Q3 shaders and using the specified file name, but this is a big improvement.
This also fixes a few glow maps in nexcompat, which are originally Q3 textures that were not renamed to _glow."

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12573 d7cf8633-e32d-0410-b094-e92efae38249