Toolbar API (was PersistStream typing changes)

[Joe Shaw <joe helixcode com>]

> This is presumably going to break many things outside of Bonobo as
> well. Given that, is there anything else we want to break at the same
> time? :)

I vote we break the API for toolbars ever-so-slightly so that we can have
toggle buttons with pixmaps. Mike committed something to allow this
yesterday, but it doesn't change the toolbar API. Using the GnomeUIInfo
is, in my opinion, absolutely atrocious and ugly for this kind of stuff.
Besides, I'm not sure I know of any other applications that use toggle
buttons in their toolbars as it stands, and it's better to fix this before
everyone starts. :)

Joe