PR libstdc++/50862
	* include/std/condition_variable (condition_variable_any::wait): Fix
	deadlock and ensure _Lock::lock() is called on exit.
	(condition_variable_any::native_handle): Remove, as per LWG 1500.
	* testsuite/30_threads/condition_variable_any/50862.cc: New.

From-SVN: r180446