Instead of re-initializing with a new instance, could this be changed to instead explicitly re-seeding the existing `Rng` instance with data from the OS?

Right now it's not entirely clear that creating a new instance is again re-seeding because you have to remember that it's got a random seed by default on `new()`. I'm also not totally in favor of `new` reading from OS randomness by default, but I'll have to go back and re-evaluate that.