Support for auto-identification of PRNG algorithm

At first, I didn't think this was going to be possible, but it actually will be in many cases. Turns out that different PRNGs produce numbers with distinctive features. Notably modulo size.

glibc rand() makes 31 bit integers
windows libc rand() makes 16 bit integers
MT makes 32 bit integers

Different MT variants will appear the same, but that's still useful. Especially since the detection is so easy.