* config/abi/pre/gnu.ver: Adjust basic_ostream exports.
	* include/std/istream (basic_iostream(basic_iostream&&)): Pass *this
	to ostream constructor.
	* include/std/ostream (basic_ostream(basic_iostream*)): Change to take
	parameter by reference, to avoid ambiguity.
	* testsuite/27_io/basic_ostream/cons/char/null.cc: New.

From-SVN: r215510