
- ability to add a GInterface to a new GObject subclass.
- modify Glib::Type::register to allow you to create GEnum and GFlags types
  in Perl.  currently it only allows GObject types.
- need a test for the flags stuff --- 6.t?

- GEnum type for G_PRIORITY_VALUES?
- can't implement g_idle_remove_by_data because ... well, how would you
  search for the data value?
- proper cleanup for bad parameter types in Glib::Object::new?
- GValue.xs may require the ability to register handlers for new fundamental
  types, since gperl_sv_from_value and gperl_value_from_sv croak on unknown
  or unimplemented data types.
  - gperl_value_from_sv should change to void return since it croaks on error.
