[gdome] Added events to Gdome

[Raph Levien <raph acm org>]

Hi Gdomers,

   I added a basic event mechanism to Gdome. I only just started
implementing the relevant methods, but I think it's a good start. As
far as I can tell, there are no more major changes needed to the IDL
(the sliding DOM methods need to be added to MyDocument, but that's an
addition to one interface). It should be possible to just finish
implementing all the methods in gdome-xml.c.in, and have a DOM usable
for in-address-space apps.

   The level 2 event stuff is Not Beautiful. With all the bubbling and
many different kinds of events, one can expect performance to be a bit
slow. But: first api, second stability, third speed.

Raph