changed behavior of r_showtris (now only affects geometry in the game view, not sky...

changed behavior of r_showtris (now only affects geometry in the game view, not sky, not hud, and not bloom)
added r_showtris_polygonoffset (doesn't seem to work, for unknown reasons)
renamed r_drawcollisionbrushes to r_showcollisionbrushes and got rid of its mode 2 behavior (which was trippy but not all that useful)
added r_showdisabledepthtest cvar which disables depth testing on the debugging geometry produced by r_show* cvars
renamed r_shadow_visiblelighting/volumes cvars to r_showlighting/shadowvolumes (and they no longer have a mode 2, use r_showdisabledepthtesting to get the same effect instead)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@6002 d7cf8633-e32d-0410-b094-e92efae38249