Cross-platform Consistent PRNG

[agroce]

Right now we just use the standard C random library, but really it'd be nice if the brute force fuzzer could do consistent tests across platforms, for various purposes. We probably need our own PRNG, something like:

https://www-cs-faculty.stanford.edu/~knuth/news02.html#rng

or

https://github.com/cmcqueen/simplerandom

I'm not sure what's best. We'd like decentish quality, maybe, and definitely speed.

This could also help with cases where the SUT does srand and uses the C PRNG!