[gtkmm] Example of Gtk::TreeModel derivation and encapsulation

[Benjamin Dauvergne <feanor-list tol-eressea org>]

I discussed with murrayc on IRC about TreeModel

I tried to make a very general base class to transforme any class into a
flat Gtk::TreeModel(equivalent to Gtk::TreeStore) the prerequisite is
that the data are easily integer indexable, it's simpler than an
iterator.

The code is here: http://benjamin.dauvergne.free.fr/gtkmm/
My goal is to add drag&drop support to this class, then to try to create
another one with n-ary tree semantic instead of integer indexed list
semantic.

I don't use the CVS version of Gtkmm, does-the vfunc for drag&drop in
Gtk::TreeDragSource and Gtk::TreeDragDest dhave been rewritten to use
Gtk::SelectionData instead of GtkSelectionData?

@+