remove the vertical scrollbar completely if the control is empty

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38917 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/vscroll.h

@@ -188,6 +188,9 @@ protected:
     // update the thumb size shown by the scrollbar
     void UpdateScrollbar();
 
+    // remove the scrollbar completely because we don't need it
+    void RemoveScrollbar();
+
 private:
     // common part of all ctors
     void Init();