mark all dtors which are virtual because base class dtor is virtual explicitly virtual themselves

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41020 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/dialup.cpp

@@ -73,7 +73,7 @@ class WXDLLEXPORT wxDialUpManagerImpl : public wxDialUpManager
 {
 public:
    wxDialUpManagerImpl();
-   ~wxDialUpManagerImpl();
+   virtual ~wxDialUpManagerImpl();
 
    /** Could the dialup manager be initialized correctly? If this function
        returns false, no other functions will work neither, so it's a good idea