Ensure that the selected item is fully visible in wxListbook

Call EnsureVisible() after re-arranging the items as otherwise the current
item could be only partly visible, at least with wxMSW wxListCtrl.

src/generic/listbkg.cpp

@@ -165,8 +165,14 @@ void wxListbook::OnSize(wxSizeEvent& event)
     // the other one is not accounted for in client size computations)
     wxListView * const list = GetListView();
     if ( list )
+    {
         list->Arrange();
 
+        const int sel = GetSelection();
+        if ( sel != wxNOT_FOUND )
+            list->EnsureVisible(sel);
+    }
+
     event.Skip();
 }