Fix point discard on non-nivida hardware
Fix point discard on non-nivida hardware

Setting gl_PointSize = 0 on nvidia hardware causes no fragments to be
generated, but this doesn't seem to work on ATI and intel cards.

rotorliu/displaz,JoshChristie/displaz,JoshChristie/displaz,JoshChristie/displaz,rotorliu/displaz,JoshChristie/displaz,JoshChristie/displaz,rotorliu/displaz,rotorliu/displaz