modified Q1BSP loader to generate lightmap fragments on its own, rather than relying...

modified Q1BSP loader to generate lightmap fragments on its own, rather than relying on the texture manager, this greatly shortens r_texturestats reports and reduces memory usage a bit (less gltexture_t structures), and modified R_UpdateTexture to be able to update fragments

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@6155 d7cf8633-e32d-0410-b094-e92efae38249