Add __is_nothrow_swappable and take it into use.

Add __is_nothrow_swappable and take it into use.

2015-06-04  Ville Voutilainen  <ville.voutilainen@gmail.com>

	Add __is_nothrow_swappable and take it into use.
	* include/bits/algorithmfwd.h (swap): Only declare for C++98 mode.
	* include/bits/move.h (swap): Add constraints in C++11 and later.
	* include/bits/stl_pair.h (swap): Use __is_nothrow_swappable
	for the free swap function for pair.
	* include/bits/stl_queue.h (swap): Use __is_nothrow_swappable
	for the free swap functions for queue and priority_queue.
	* include/bits/stl_stack.h (swap): Use __is_nothrow_swappable
	for the free swap function for stack.
	* include/debug/array (swap): Use __is_nothrow_swappable
	for the free swap function for array.
	* include/profile/array (swap): Likewise.
	* include/std/array (swap): Likewise.
	* include/std/tuple (_Tuple_impl::_M_swap): Use __is_nothrow_swappable.
	* include/std/type_traits (__is_swappable_impl::__is_swappable,
	__is_nothrow_swappable_impl, __is_nothrow_swappable): New.
	* testsuite/20_util/is_nothrow_swappable/requirements/
	explicit_instantiation.cc: New.
	* testsuite/20_util/is_nothrow_swappable/requirements/typedefs.cc:
	New.
	* testsuite/20_util/is_nothrow_swappable/value.cc: New.

From-SVN: r224153