DestroyNotify for Bonobo callbacks

[John Sullivan <sullivan eazel com>]

There doesn't seem to be any DestroyNotify handling for Bonobo menu and
toolbar callbacks, making it very difficult to pass any callback data
that needs freeing. Am I missing something, or is this a hole in the
API? Is there any reason why such a feature shouldn't be added to
Bonobo? Darin has volunteered to add such a feature unless there's some
sensible reason not to.

John