[Bug c++/102177] Implement C++17 P0418R2

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102177

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51406
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51406&action=edit
gcc12-pr102177.patch

Untested patch to remove the warning and just use maximum for success if weaker
than failure instead of always seq_cst.

On the other side, even current C2X draft has that:
The failure argument shall be no stronger than the success argument.
requirement.  So should we keep the restriction for __atomic_* APIs and just
pass maximum from libstdc++ headers?