Faster raytracing using TinyBVH

[BrunoLevy]

Make the "Raytracing" shader faster using TinyBVH
From my first test, it seems that it can be around 10x faster !

• first interfacing (in fact, 3x to 5x faster)
• copy everything to array of triangles, colors and/or normals
• use the function with packets of 256 rays
• try also fvpw and compare (suggested by Jesse Louis-Rosenberg)