lightmap update checking is now handled very differently; each brush model has a...

lightmap update checking is now handled very differently; each brush model has a set of lightmap chains for each light style, and they are marked if the light style's value changes, similarly dlights mark surfaces they touch as well...  both use surf->cached_dlight...  this doesn't seem to be a speed gain (or loss) at present, but allows further restructuring which should be a speed gain

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@2630 d7cf8633-e32d-0410-b094-e92efae38249