This basically removes the "adv" library, even though it's still
preserved for compatibility with user make/project files referring to
it.
It is done because the distinction between "adv" and "core" was never
really clear (e.g. why wxTreeCtrl was in core but wxTreeListCtrl in
adv?) and it prevented some core classes from using adv ones.
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