Final commit before creating new branch for beta doubling.

I have done a fair amount of testing that seems to show that this code (MTRand, especially) works the same on all machines and with all compilers. The primary problems that remain are:
1) Dimer correlation estimator just does not generate accurate results.
2) Simulation seems to get easily stuck in metastable states, especially magnetization sectors. Like S=0 when it should be S=1, for example. It stays in these metastable states for a long time, up to at thousand MC steps. Usually there are exactly zero fluctuations in magnetization. Hopefully beta doubling will help solve this.