add wrapper for boost::mt19937 mersenne twister rng

The class mt_rng is a wrapper which provides a similar interface to
this boost rng class as we had to the linear congruential rng
implemented in simple_rng. This commit creates mt_rng.hpp and
mt_rng.cpp and adds them to SConscript and CMakeLists.
switch over gamestatus and sync code to use mt_rng

In place where previously simple_rng was being used.