2. changed it to use wxSubwindows to cut down code duplication
3. deprecated Get/SetNumberOfRowsOrCols() which didn't do anything in neither
MSW nor GTK (this is the only change in GTK code)
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@30980 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775