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/sound.cpp

@@ -296,7 +296,7 @@ class wxSoundSyncOnlyAdaptor : public wxSoundBackend
 public:
     wxSoundSyncOnlyAdaptor(wxSoundBackend *backend)
         : m_backend(backend), m_playing(false) {}
-    ~wxSoundSyncOnlyAdaptor()
+    virtual ~wxSoundSyncOnlyAdaptor()
     {
         delete m_backend;
     }