D: Work around nativepointer problem in test-suite/typemap_directorout.i.

Just "%typemap(ddirectorout) MyType &USEME = SWIGTYPE &;" does not
inherit the antivepointer attribute from the SWIGTYPE & case, but
the other typemaps that are not overridden (dout/…). Thus, some
of the emitted code used native pointers, and some SWIGTYPE_p_int.