GtkTree*

[jrb redhat com]

I just committed the new GtkTree class of widgets to CVS.  It should be
useable at a basic level now, and I'd love some "real-world" API
feedback if anyone would like to play with it.  Additionally, I ran into
a name-space conflict when I checked it in -- GTK_TREE_SELECTION is used
in both by GtkTree (the old widget) and GtkTreeSelection (the new one.)
I'd like to rename the old macro, as it's barely used anywhere and we'd
like to get people to stop using the old GtkTree widget, anyways, but
I'd like to hear any objections people have before I do so.

Thanks,
-Jonathan