Added r_cullentities_trace_expand and pad cvars, these configure additional ways...

Added r_cullentities_trace_expand and pad cvars, these configure additional ways to expand entity boxes when culling by traceline.

Added r_vis_trace feature which allows you to turn on traceline-based culling of portals, and r_vis_trace_surfaces lets you cull surfaces by traceline (slow and probably pointless, but a curious feature).

Added r_shadow_culllights_trace_expand and pad cvars.

Added sv_cullentities_trace_expand to make SV_CanSeeBox be at feature parity with R_CanSeeBox.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12395 d7cf8633-e32d-0410-b094-e92efae38249