SubdivideCleanBenchmark times are untouched with this change, but the
hash should be better for MeshTools::CombineIndices, where the previous
hash generated all zeros in most cases.
Algorithm used: Pedro V. Sander, Diego Nehab, and Joshua Barczak, Fast
Triangle Reordering for Vertex Locality and Reduced Overdraw, SIGGRAPH
2007, http://gfx.cs.princeton.edu/pubs/Sander_2007_%3ETR/index.php
Also created new shared MeshTools library.