* include/std/functional (__invoke_impl): New overloads.
(__invoke): Replace with a single function calling __invoke_impl.
(invoke): Add C++17 std::invoke.
(reference_wrapper::operator()): Qualify call to __invoke.
(_Mem_fn_traits_base, _Mem_fn_traits): Remove unused typedefs.
(_Mem_fn_base): Remove unused typedefs and implement call operator in
terms of __invoke.
* include/std/future (__future_base::_Async_state_commonV2): Do not
pass reference_wrapper as object argument to call_once.
* include/std/type_traits (result_of): Define nested __invoke_type.
Handle reference_wrapper as per LWG 2219.
* testsuite/20_util/bind/ref_neg.cc: Adjust dg-error directives.
* testsuite/20_util/function_objects/mem_fn/55463.cc: Remove tests
using member functions of reference_wrapper.
From-SVN: r229290
