- the ability to create new GSources in Perl could be handy, and wouldn't be
hard to implement (a hash in place of GSourceFuncs).
- 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?
- would require either iterating over the list twice or cleaning up before
the croak. the latter is probably the way to go.
- there is no way to clean up if gperl_sv_from_value() fails.
- gperl_value_from_sv should change to void return since it croaks on error.
(can't do this without breaking ABI)