Fix c++ compiler warnings in c++11 testcases

Examples/test-suite/cpp11_final_override.i

@@ -82,6 +82,7 @@ struct Destructors4 : Base {
 struct FinalOverrideMethods {
     virtual void final() {}
     virtual void override(int) {}
+    virtual ~FinalOverrideMethods() = default;
 };
 struct FinalOverrideVariables {
     int final;