PR libstdc++/50196
	* acinclude.m4 (GLIBCXX_HAS_GTHREADS): Don't depend on _POSIX_TIMEOUTS.
	* configure: Regenerate.
	* include/std/mutex (timed_mutex, recursive_timed_mutex): Define
	conditionally on GTHREADS_HAS_MUTEX_TIMEDLOCK.
	* testsuite/lib/libstdc++.exp (check_v3_target_gthreads_timed): Define.
	* testsuite/lib/dg-options.exp (dg-require-gthreads-timed): Define.
	* testsuite/30_threads/recursive_timed_mutex/dest/destructor_locked.cc:
	Use dg-require-gthreads-timed instead of dg-require-gthreads.
	* testsuite/30_threads/recursive_timed_mutex/native_handle/
	typesizes.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/native_handle/1.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock_until/1.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock_until/2.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/cons/assign_neg.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/cons/1.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/cons/copy_neg.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/requirements/typedefs.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock/1.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock/2.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/lock/1.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/lock/2.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/unlock/1.cc: Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock_for/1.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock_for/2.cc:
	Likewise.
	* testsuite/30_threads/recursive_timed_mutex/try_lock_for/3.cc:
	Likewise.
	* testsuite/30_threads/timed_mutex/dest/destructor_locked.cc: Likewise.
	* testsuite/30_threads/timed_mutex/native_handle/typesizes.cc:
	Likewise.
	* testsuite/30_threads/timed_mutex/native_handle/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock_until/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock_until/2.cc: Likewise.
	* testsuite/30_threads/timed_mutex/cons/assign_neg.cc: Likewise.
	* testsuite/30_threads/timed_mutex/cons/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/cons/copy_neg.cc: Likewise.
	* testsuite/30_threads/timed_mutex/requirements/standard_layout.cc:
	Likewise.
	* testsuite/30_threads/timed_mutex/requirements/typedefs.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock/2.cc: Likewise.
	* testsuite/30_threads/timed_mutex/lock/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/unlock/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock_for/1.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock_for/2.cc: Likewise.
	* testsuite/30_threads/timed_mutex/try_lock_for/3.cc: Likewise.
	* testsuite/30_threads/unique_lock/cons/5.cc: Likewise.
	* testsuite/30_threads/unique_lock/cons/6.cc: Likewise.
	* testsuite/30_threads/unique_lock/locking/3.cc: Likewise.
	* testsuite/30_threads/unique_lock/locking/4.cc: Likewise.

From-SVN: r180329