* include/std/mutex (scoped_lock): Reorder std::adopt_lock_t parameter
	as per P0739R0.
	* testsuite/30_threads/scoped_lock/cons/1.cc: Reorder arguments.
	* testsuite/30_threads/scoped_lock/cons/deduction.cc: Test deduction
	with std::adopt_lock_t.
	* testsuite/30_threads/scoped_lock/requirements/typedefs.cc: Check
	feature-test macro.

From-SVN: r250223