unified model skinframe loaders used for mdl, md2, md3, and bsp textures (both extern...

unified model skinframe loaders used for mdl, md2, md3, and bsp textures (both external and internal where applicable)
imageskin_t and image_loadskin/image_freeskin functions added to image.[ch] for use by the unified skinframe loaders
added palette_nocolormap
split r_shadow_bumpscale cvar into r_shadow_bumpscale_bumpmap (for _bump textures) and r_shadow_bumpscale_basetexture (self explanatory)
now loads _norm normalmap textures (tenebrae compatibility)
_nmap normalmap texture support removed (it was broken in the previous release and I don't need to bog down the texture loader with even more unnecessary names)
r_shadow_lightattenuationpower added (default 2, to leave it looking identical to previous versions, this controls the falloff curve of light)
renamed detailtextures array to mod_shared_detailtextures and moved it and related code to model_shared.[ch]
removed progs/missile.mdl shadow casting check (in r_shadow_realtime mode) I had forgotten to remove before committing last time

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@2682 d7cf8633-e32d-0410-b094-e92efae38249