Blind fixes for warnings in wxTinderbox.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@37168 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/univ/scrarrow.h

@@ -81,6 +81,8 @@ private:
 class WXDLLEXPORT wxControlWithArrows
 {
 public:
+    virtual ~wxControlWithArrows() {}
+
     // get the renderer to use for drawing the arrows
     virtual wxRenderer *GetRenderer() const = 0;