libstdc++: Specialize copy/copy_n for istreambuf_iterator and deque iterators

libstdc++: Specialize copy/copy_n for istreambuf_iterator and deque iterators

Add __copy_n_a overloads for std::deque iterators to replace with C memmove
when possible. Expose std::copy_n implementation details in pre-C++11 modes
and use it for std::copy overloads.

libstdc++-v3/ChangeLog

	* include/bits/stl_algo.h (__copy_n_a): Move to ...
	* include/bits/stl_algobase.h (__copy_n_a): ...here. Add __strict
	parameter.
	(__copy_n_a(istreambuf_iterator<>, _Size, _Deque_iterator<>, bool)):
	Declare.
	(__niter_base(const _Safe_iterator<_Ite, _Seq,
	random_access_iterator_tag>&)): Declare.
	(__copy_move_a2(istreambuf_iterator<>, istreambuf_iterator<>,
	_Deque_iterator<>)): Declare.
	* include/bits/deque.tcc
	(__copy_move_a2(istreambuf_iterator<>, istreambuf_iterator<>,
	_Deque_iterator<>)): New.
	(__copy_n_a(istreambuf_iterator<>, _Size, _Deque_iterator<>, bool)):
	New.
	* include/bits/streambuf_iterator.h
	(__copy_n_a(istreambuf_iterator<>, _Size, _CharT*, bool)): Adapt.
	* include/debug/safe_iterator.tcc (__niter_base): New.
	* testsuite/25_algorithms/copy/streambuf_iterators/char/4.cc
	(test03): New.
	* testsuite/25_algorithms/copy/streambuf_iterators/char/debug/deque_neg.cc:
	New test.
	* testsuite/25_algorithms/copy_n/debug/istreambuf_ite_deque_neg.cc:
	New test.
	* testsuite/25_algorithms/copy_n/istreambuf_iterator/2.cc: New test.
	* testsuite/25_algorithms/copy_n/istreambuf_iterator/deque.cc:
	New test.