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

[mimomorin at gmail dot com]

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

--- Comment #18 from Michel Morin <mimomorin at gmail dot com> ---
Thanks, much appreciated!

(In reply to Jonathan Wakely from comment #17)
> That's how new features work. If you want to use them, you need the new
> version. The time for adding new features to GCC 9 was last year.

Agreed in general. If this was a C++2A feature, I would not ask for releasing
it in a hurry. New features should be tested enough and we developers can
test/use the feature with a gcc-trunk snapshot. (I made this backport request
because I (mistakenly) thought that this was a small fix and not a new
feature.)