WIP: Store a default_rng const which can be changed if the default RNG c...

...hanges in the future

Based on a comment here: https://github.com/JuliaLang/julia/pull/6018

This makes the default RNG a little more explicit, and more easily reversible if we use a different one in later versions.


This slows down random number generation.

deps/random/randmtzig.c might need to change as well