[Bug libstdc++/63400] [C++11]precision of std::chrono::high_resolution_clock

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63400

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Maybe we should make high_resolution_clock a typedef for steady_clock on
mingw-w64 .... but maybe only when using winpthreads.