Fix Python 3 inconsistency handling -ve numbers for unsigned C types.

An OverFlow error is now consistently thrown instead of a TypeError.

Fixes primitive_types testcase for Python 3

Lib/python/pyprimtypes.swg

@@ -127,6 +127,18 @@ SWIG_AsVal_dec(unsigned long)(PyObject *obj, unsigned long *val)
       return SWIG_OK;
     } else {
       PyErr_Clear();
+%#if PY_VERSION_HEX >= 0x03000000
+      {
+        long v = PyLong_AsLong(obj);
+        if (!PyErr_Occurred()) {
+          if (v < 0) {
+            return SWIG_OverflowError;
+          }
+        } else {
+          PyErr_Clear();
+        }
+      }
+%#endif
     }
   }
 %#ifdef SWIG_PYTHON_CAST_MODE