cleanups in bvh_builder_subdiv.cpp, separated cached builded into subroutines
cleanups in bvh_builder_subdiv.cpp, separated cached builded into subroutines

Sjoerdie/embree,Sjoerdie/embree,embree/embree,embree/embree,embree/embree,Sjoerdie/embree,embree/embree,Sjoerdie/embree