1. wxUSE_COLLPANE added
2. XRC handler added
3. flicker fixes for the generic version
4. sizing fixes for GTK+ version
5. RTL fixes for the generic version (via wxBoxSizer)
6. better appearance under Mac for the generic version
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42759 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775