Test ability to manipulate a daughter class from its base class wrapper

Even in the case of just creating a `DerivedClass` this test says:
```
swig/python detected a memory leak of type 'DerivedClass *', no destructor found.
```
even though the destructor is defined in the base class.

Examples/test-suite/abstract_basecast.i

@@ -0,0 +1,20 @@
+%module abstract_basecast
+
+%inline %{
+class BaseClass {
+public:
+    virtual ~BaseClass() { }
+
+    virtual void g() = 0;
+};
+
+class DerivedClass : public BaseClass {
+public:
+
+    virtual void g() { }
+
+    BaseClass& f() {
+        return *this;
+    }
+};
+%}