This code provides an implementation of the PCG family of random number
generators, which are fast, statistically excellent, and offer a number of
useful features.

There are two kinds of generator, normal generators and extended generators.
Extended generators provide k dimensional equidistribution and can perform party
tricks, but generally speaking most people only need the normal generators.

There are two ways to access the generators, using a convenience typedef or by
using the underlying templates directly (similar to C++11's std::mt19937 typedef
vs its std::mersenne_twister_engine template).