[OCaml] Runtime tests for fvirtual, overload_polymorphic and some others

Add runtime tests for conversion, extend_typedef_class,
extend_constructor_destructor, fvirtual, overload_polymorphic,
template_rename, and using1.

Examples/test-suite/ocaml/overload_polymorphic_runme.ml

@@ -0,0 +1,9 @@
+open Swig
+open Overload_polymorphic
+
+let _ =
+  let t = new_Derived '() in
+  assert (_test (t) as int = 0);
+  assert (_test '(1) as int = 1);
+  assert (_test2 (t) as int = 1)
+;;