Drop the CamelCase name, and use glib output
Abandon the custom DieTree model

Use the canonical GtkTreeStore instead.  The same lazy child-expansion
is achieved with a placeholder for any dwarf_haschildren, which gets
filled in by a callback on the GtkTreeView's "row-expanded" signal.

In theory it's more wasteful for every node to carry all the Dwarf_Die-
generated metadata, instead of producing those on request, but I didn't
measure any real difference in memory usage.
Use Glade files for layout

It's not too much different yet, but hopefully as the UI gets more
complex, the Glade designer will be easier than manual C calls.
Start enumerating Dwarf_Attribute

For now, it just shows the attribute code, without any values.