New O(log(word size)) code for Z curve intersection with hyperbox

 * Profiling indicates around a 4x speedup
 * Further speedup possible with bit intrinsics
New O(log(word size)) code for X, Y to Z value computation

 * Profiling indicates around a 1.75x speedup
Rewrite the individual code to use flat arrays

 * Profiling indicates around a 1.5x speedup