Default generator initialization
Seeds the current defalt generator from the system RNG device if it is currently unseeded.
This is the closest thing to Random.self_init and is a good way to prime the RNG.
Manual seeding
val reseed : ?bytes:int -> ?device:string -> Nocrypto.Rng.g -> unitreseed ~bytes ~g mixes in bytes bytes from the system RNG into the generator g.
bytes default to a small value reasonable for periodic reseeding.
device defaults to sys_rng.