[Bug libstdc++/98034] std::atomic_signed_lock_free and std::atomic_unsigned_lock_free not defined

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98034

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #0)
> C++20 adds these typedefs.

And the __cpp_lib_atomic_lock_free_type_aliases feature test macro.