[gtkada] Sorting list/tree model

[Manuel Op de Coul]

I've never used Gtk.Tree_Model_Sort so I don't know.
But the ordering in the view is not done by defining a comparison function,
but by the values in the tree model, which can be float, integer, string.
Note that you can put extra columns in the model which are not shown in the
treeview. So if you need a different ordering, you can choose a
different column in your model, or change the values in it,
or even replace the whole model with another one.

Manuel