Python code generated with '-builtin -modernargs' segfaults for any method taking zero arguments.

Also fixes: "SystemError: error return without exception set" during error checking
when using just -builtin and the incorrect number of arguments is passed to a class
method expecting zero arguments.

Closes #256
Closes #382

Examples/test-suite/template_classes.i

@@ -18,6 +18,9 @@ class RectangleTest {
 public:
   Point<T>& getPoint() {return point;}
   void setPoint(Point<T>& value) {point = value;}
+
+  static int static_noargs() { return 0; }
+  static int static_onearg(int i) { return i; }
 private:
   Point<T> point;