Evaluate biases in generation of random floats

* https://lemire.me/blog/2017/02/28/how-many-floating-point-numbers-are-in-the-interval-01/
* https://github.com/pytorch/pytorch/issues/16706
* http://xoroshiro.di.unimi.it/random_real.c
* https://mumble.net/~campbell/2014/04/28/random_real.c

Review the linked article, PyTorch issue, and random_real.c references first, then inspect PHP-Random's float-generation entry point. Establish whether the current generation is biased and define the expected behavior or evidence needed for the issue to be considered evaluated.

Written by the indexing model from the issue text.