Update new-abi upcast algorithm.

Update new-abi upcast algorithm.

	* inc/cxxabi.h (__class_type_info::__do_upcast): Change
	prototype and meaning of return value.
	(__si_class_type_info::__do_upcast): Likewise.
	(__vmi_class_type_info::__do_upcast): Likewise.
	* tinfo.cc (__class_type_info::__upcast_result): Replace
	whole2dst with part2dst. Adjust ctor.
	(__class_type_info::__do_upcast): Adjust call of worker function.
	(__class_type_info::__do_upcast): Adjust.
	(__si_class_type_info::__do_upcast): Adjust. Use parent's
	__do_upcast.
	(__vmi_class_type_info::__do_upcast): Likewise. Fix private
	virtual base in diamond heirarchy bug.

From-SVN: r34132