added r_shadow_showtris

added r_shadow_showtris
added gl_texture_anisotropy to menu
changed sv_cullentities_trace and _pvs defaults to 0 and 1 respectively (now uses pvs culling because trace culling was too slow in q3bsp)
r_shadow_realtime_world now works in q3bsp (using upgraded Mod_ShadowMesh functions to combine lighting meshes)
rewrote most of R_Q3BSP_DrawFace - now supports singletexture cards, r_shadow_realtime_world, and glow textures

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@3623 d7cf8633-e32d-0410-b094-e92efae38249