BlaBla counter-based crypto rng

[gahtan-syarif]

JP Aumasson (creator of Blake2 and SipHash) created a 64-bit version of ChaCha he called BlaBla (https://github.com/veorq/blabla/blob/master/BlaBla.swift). I've tested it using C++ and it seems that it can run at speeds almost 2x of that of chacha with the same number of rounds on a 64-bit system. Perhaps its worth adding to randomgen?

I've created a c++ implementation of it here: https://github.com/gahtan-syarif/blabla.h