refactored and optimized the R_Q1BSP_RecursiveGetLightInfo function

refactored and optimized the R_Q1BSP_RecursiveGetLightInfo function
properly clear the leaf, surface, and triangle visibility data on a
light, this might fix performance issues with the SVBSP culling method
added a BIH (bounding interval hierarchy) culling method for lights
rather than just the BSP method used by default, however this has
yielded no performance gains outside of .obj maps, so by default it only
uses this new method on .obj maps (where the lack of vis culling is
unimportant)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@10624 d7cf8633-e32d-0410-b094-e92efae38249