add interp_v3_v3v3v3_uv() to use for use with uv value from isect_ray_tri_v3(), rename tree -> bmtree for BMBVHTree.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56102 954f8c5b-7b00-dc11-b283-0030488c597c