PR libstdc++/49204

	PR libstdc++/49204
	* include/std/future (__future_base::_State_base): Rename to
	__future_base::_State_baseV2.
	(__future_base::_State_baseV2::~_State_baseV2): Define as defaulted.
	(__future_base::_State_baseV2::_M_run_deferred): Rename to
	_M_complete_async.
	(__future_base::_State_baseV2::_M_has_deferred): Add new virtual.
	(__future_base::_State_baseV2::wait_for): Call _M_has_deferred() to
	test for a deferred function, or call _M_complete_async() to join an
	async thread that has made the shared state ready.
	(__future_base::_State_baseV2::wait_until): Likewise.
	(__future_base::_Async_state_common): Rename to _Async_state_commonV2.
	(__future_base::_Async_state_commonV2::_M_run_deferred): Rename to
	_M_complete_async.
	* src/c++11/compatibility-thread-c++0x.cc (__future_base::_State_base):
	Export old definition.
	(__future_base::_Async_state_common): Likewise.
	* src/c++11/future.cc (__future_base::_State_base::~_State_base):
	Remove.
	* doc/xml/manual/status_cxx2011.xml: Update status.
	* testsuite/30_threads/async/async.cc: Test future_status::timeout
	and future_status::ready.
	* testsuite/30_threads/async/sync.cc: Test future_status::deferred.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@205144 138bc75d-0d04-0410-961f-82ee72b054a4