test if a triangle (id) is rejected:

	Implicitly, id is used in macro NV

  mark =  testNode(V(NV(0)),V(NV(1)),V(NV(2)));

testNode takes SpatialVectors and returns reject, full, partial or dontknow
it would make more sense to have a testnode(id) and macros have no implicit reference to id

OPTIMIZE:
	The expresiion index->nodes_[id] gets evaluated three times, instead of once.


testNode(
	index->vertices_[ index->nodes_[id].v_[0]]
	index->vertices_[ index->nodes_[id].v_[1]]
	index->vertices_[ index->nodes_[id].v_[2]]

This simple thing  took the runtime from 6.36 to 6.24 (time intersect -count -range 14 ex4)

INTERESTING TRIVIA:
	in gnu C++, references are slower than pointers

  // Slow: const struct SpatialIndex::QuadNode &indexNode = index_->nodes_[id];
  const struct SpatialIndex::QuadNode *indexNode = &index_->nodes_[id]; //faster 
