message: g++ 5.4 compile fix
diff: @@ -71,7 +71,7 @@ struct hit_record_bvh_inst : hit_record_bvh<R, Base>
  int_type inst_id = int_type(0);
  // Inverse transformation matrix
  - matrix<4, 4, scalar_type> transform_inv = matrix<4, 4, scalar_type>::identity();
  + matrix<4, 4, scalar_type> transform_inv = matrix<4, 4, typename R::scalar_type>::identity();
  };
  