spearmint: Fix dlights in OpenGL1 not always affecting world

BSP flares in leafs cause surfaces after it not to be added to bounds
(surfMins and surfMaxs) used by dlight culling code from ET.

continue is run, but mark++ is not. This causes the flare to be checked
again instead of the the next surface.
spearmint: Cleanup GL2 R_SetParent function

Make it more similar to the GL1 code. Also mark++ isn't needed in GL2.