Replace std::result_of with std::invoke_result, as specified in the
standard since C++17, to avoid deprecated warnings for std::result_of.
We don't have __invoke_result_t in C++11 mode, so add it as an alias
template for __invoke_result<>::type (which is what std::result_of uses
as its base class, so there's no change in functionality).
This fixes warnings given by Clang 18.
libstdc++-v3/ChangeLog:
PR libstdc++/114394
* include/std/functional (bind): Use __invoke_result_t instead
of result_of::type.
* include/std/type_traits (__invoke_result_t): New alias
template.
* testsuite/20_util/bind/ref_neg.cc: Adjust prune pattern.
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