[Help-smalltalk] small visualgst steps

[Paolo Bonzini]

I pushed some further changes to the commandmenu branch.

In particular I finished conversion to GtkScrollTreeWidget for a good 
part of the widgets.  I also made MenuBuilder a first-class citizen 
rather than a class-method-only class.

I don't plan to do much more work on commandmenu until I finish 
new-state branch, which is now based on top of commandmenu.  The first 
step is still the same, i.e. convert inspectors and debuggers to run 
inside a GtkShell.  After that, it will be time to add dynamic menus and 
toolbars using the Command/MenuBuilder infrastructure.

Please pull.

Paolo