[Bug libstdc++/78870] Support std::filesystem on Windows

[development at jordi dot vilar.cat]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78870

--- Comment #19 from Jordi Vilar <development at jordi dot vilar.cat> ---
(In reply to Jonathan Wakely from comment #18)
> That was already done two weeks ago by r260479

Thank you! And a last question: Do you plan to merge both patches into the gcc
8 branch?