made wxTreeTraversal and wxIDropSources dtors virtual (patch 1311828)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@36251 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/ole/dropsrc.cpp

@@ -53,6 +53,7 @@ class wxIDropSource : public IDropSource
 {
 public:
   wxIDropSource(wxDropSource *pDropSource);
+  virtual ~wxIDropSource() { }
 
   DECLARE_IUNKNOWN_METHODS;
 

src/msw/treectrl.cpp

@@ -311,6 +311,11 @@ public:
         m_tree = tree;
     }
 
+    // give it a virtual dtor: not really needed as the class is never used
+    // polymorphically and not even allocated on heap at all, but this is safer
+    // (in case it ever is) and silences the compiler warnings for now
+    virtual ~wxTreeTraversal() { }
+
     // do traverse the tree: visit all items (recursively by default) under the
     // given one; return true if all items were traversed or false if the
     // traversal was aborted because OnVisit returned false