SFINAE for overload resolution of intersect(bvh)
SFINAE for overload resolution of intersect(bvh)

Ensure that this overload is only used for bvhs

tu500/visionaray,ukoeln-vis/ctpperf,tu500/visionaray,szellmann/visionaray,ukoeln-vis/ctpperf,szellmann/visionaray