[Bug libstdc++/87431] valueless_by_exception() should unconditionally return false if all the constructors are noexcept

[antoshkka at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87431

--- Comment #2 from Antony Polukhin <antoshkka at gmail dot com> ---
New intrinsic could be added into the GCC... something like
__builtin_all_constructors_nothrow(type)