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.cxx

@@ -0,0 +1,28 @@
+/* File : example.cxx */
+
+#include "example.h"
+#define M_PI 3.14159265358979323846
+
+/* Move the shape to a new location */
+void Shape::move(double dx, double dy) {
+  x += dx;
+  y += dy;
+}
+
+int Shape::nshapes = 0;
+
+double Circle::area() {
+  return M_PI*radius*radius;
+}
+
+double Circle::perimeter() {
+  return 2*M_PI*radius;
+}
+
+double Square::area() {
+  return width*width;
+}
+
+double Square::perimeter() {
+  return 4*width;
+}