libstdc++: Implement std::atomic::fetch_min/max

This patch extends libstdc++ to implement C++26's atomic fetch min/max
operations.

The __atomic_fetch_minmaxable concept checks if __atomic_fetch_min and
__atomic_fetch_max builtins are implemented by the compiler. If not, fall back
to a CAS loop.

This patch was bootstrapped and regtested on aarch64-linux-gnu and
x86_64-linux-gnu, no regression.

Signed-off-by: Soumya AR <soumyaa@nvidia.com>

libstdc++-v3/ChangeLog:

	* include/bits/atomic_base.h:
	Add fetch_min and fetch_max memberfunctions.
	* include/bits/version.def:
	Add __cpp_lib_atomic_min_max feature test macro.
	* include/bits/version.h (defined): Regenerate.
	* include/std/atomic: Extend for fetch_min/max non-member functions.
	* src/c++23/std.cc.in: Export atomic_fetch_min, atomic_fetch_max,
	atomic_fetch_min_explicit, atomic_fetch_max_explicit.
	* testsuite/29_atomics/atomic_integral/nonmembers_fetch_minmax.cc:
	New test.
	* testsuite/29_atomics/atomic_ref/integral_fetch_minmax.cc: New test.

0 files changed, 0 insertions, 0 deletions