Fix mzscheme static variable wrappers

$argnum needs to be expanded in the 'varin' typemap which shares
code used by the 'in' typemap.
Setting the static variable is also a function call (argnum=1).

Added class examples - needs static variables to work
Test newly working test cases with this fix

Examples/mzscheme/class/example.h

@@ -0,0 +1,34 @@
+/* File : example.h */
+
+class Shape {
+public:
+  Shape() {
+    nshapes++;
+  }
+  virtual ~Shape() {
+    nshapes--;
+  }
+  double  x, y;
+  void    move(double dx, double dy);
+  virtual double area() = 0;
+  virtual double perimeter() = 0;
+  static  int nshapes;
+};
+
+class Circle : public Shape {
+private:
+  double radius;
+public:
+  Circle(double r) : radius(r) { }
+  virtual double area();
+  virtual double perimeter();
+};
+
+class Square : public Shape {
+private:
+  double width;
+public:
+  Square(double w) : width(w) { }
+  virtual double area();
+  virtual double perimeter();
+};