[Gtk-sharp-list] .Dispose and warnings on quit.

[Todd Berman]

The current implementation of .Dispose for any GObject wrapper doesn't
appear to be unhooking signal handlers.

Also, what is the proper thing to call, .Dispose or .Destroy? I do
understand that .Dispose is a .net construct where as .Destroy is a gtk+
construct. Right now we seem to offer two paths to do very similar
operations, and it seems like we should be offering one coherent
solution.

--Todd