re PR libstdc++/57394 ([C++11] basic_streambuf incorrect copy constructor / copy assignment access specifier)

	PR libstdc++/57394
	* include/bits/ios_base.h (ios_base(const ios_base&)): Define as
	deleted for C++11.
	(operator=(const ios_base&)): Likewise.
	* include/std/streambuf: Remove trailing whitespace.
	(basic_streambuf(const basic_streambuf&)): Fix initializer for
	_M_out_end. Define as defaulted for C++11.
	(operator=(const basic_streambuf&)): Define as defaulted for C++11.
	(swap(basic_streambuf&)): Define for C++11.
	* testsuite/27_io/basic_streambuf/cons/57394.cc: New.

From-SVN: r210228