Lib/Octave: in Octave >= 4.4, assign reference to base class in subclass

- See Examples/octave/callback/runme.m: a.run() calls Octave callback,
  but due to changes in behaviour to subsref() a.Callback.run() can no
  longer be used to call C callback unless a.Callback actually exists;
  subsrefs() just gets the "Callback" call whereas prior to Octave 4.4
  it would get both the "Callback" and "run" calls. So now a.Callback is
  set to the original base class (with own=0) so that it can be accessed

Lib/octave/octrun.swg

@@ -484,8 +484,12 @@ SWIGRUNTIME void swig_acquire_ownership_obj(void *vptr, int own);
       }
       types.insert(types.end(), rhs.types.begin(), rhs.types.end());
       members.insert(rhs.members.begin(), rhs.members.end());
+#if SWIG_OCTAVE_PREREQ(4,4,0)
+      assign(rhs.swig_type_name(), rhs.as_value());
+#else
       rhs.types.clear();
       rhs.members.clear();
+#endif
     }
 
     typedef member_map::const_iterator swig_member_const_iterator;