Initialization changes

[Andy Wingo]

Some further GOOPSification,

There's no more gtype-instance:initialize. Instead we override
make-instance for <gtype-instance-class>es, so that we don't actually
call `initialize'. Then when GObject comes around to do its
initialization, it calls `initialize'. But if that's confusing, just
know that gtype-instance:initialize is gone.

Also I made a new function, `especify-metaclass!'. It takes an existing
gtype-class and makes its metaclass more specific. This is somewhat
hackish, I think, but it could form the basis of a new
define-class-method whose first argument would be a class that would
then be especified. Anyway it serves to modify gtype-classes after they
are created so you can dispatch on the classes.

I also finished the changes recommended by Andreas, but I hope they're
not necessary for long ;)

Regards,

wingo.

p.s. Guile-GStreamer is up to date again with HEAD GStreamer, and can
also build against the stable 0.6 branch.