re PR libstdc++/54297 ([C++11] Segmentation fault with std::async and released shared...

re PR libstdc++/54297 ([C++11] Segmentation fault with std::async and released shared state)

	PR libstdc++/54297
	* include/std/future (~_Async_state_impl): Join thread before
	derived class members are destroyed.
	(~_Async_state_common): Only define non-trivial destructor when
	included from future.cc for ABI compatibility reasons.
	* src/c++11/future.cc (_GLIBCXX_ABI_COMPAT_ASYNC): Define.
	* testsuite/30_threads/async/54297.cc: New.

From-SVN: r190672