libstdc++: Implement std::clamp with std::min and std::max [PR 96733]

libstdc++: Implement std::clamp with std::min and std::max [PR 96733]

The compiler doesn't know about the precondition of std::clamp that
(hi < lo) is false, and so can't optimize as well as we'd like. By using
std::min and std::max we help the compiler.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:

	PR libstdc++/96733
	* include/bits/stl_algo.h (clamp): Use std::min and std::max.