implement GetSizeAvailableForScrollTarget

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@56204 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/dataview.h

@@ -490,6 +490,7 @@ private:
 
 private:
     void OnSize( wxSizeEvent &event );
+    virtual wxSize GetSizeAvailableForScrollTarget(const wxSize& size);
 
     // we need to return a special WM_GETDLGCODE value to process just the
     // arrows but let the other navigation characters through