[Bug libstdc++/85494] implementation of random_device on mingw is useless

[dmjpp at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85494

--- Comment #6 from Dimitrij Mijoski <dmjpp at hotmail dot com> ---
I read the patch couple of times and seems completely OK. Can you push it to
the repository (or to a fork)?