re PR libstdc++/63840 (std::function copy constructor deletes an uninitialized pointer if new fails)

	PR libstdc++/63840
	* include/std/functional (function::function(const function&)): Set
	_M_manager after operations that might throw.
	* include/tr1/functional (function::function(const function&),
	function::function(_Functor, _Useless)): Likewise.
	* testsuite/20_util/function/63840.cc: New.
	* testsuite/tr1/3_function_objects/function/63840.cc: New.

From-SVN: r218215