Removing and adding headers, letting the view update itself

[Philip Van Hoof <spam pvanhoof be>]

It is now possible to append and prepend items to the header model using
the TnyListIface. The GtkTreeView will update itself automatically.

It's not yet bugfree to also remove items. There's something strange
happening if you remove items starting from the 3th row. I have to check
what's happening first. I' guessing I'll get this to work soon.

Also note that I've also tested REUSING the GtkTreeModel instance. As
long as you only append or prepend, this does work. It's a little bit
unstable in terms of locking issues ... but I'll get to that.

-- in some rare cases, you might get a deadly embrace lock if you reuse
the same model. This probably has something to do with clearing the
previous set of headers .. while loading the new set of headers.

Note that reusing the model will not magically make things a lot faster.
It's just another way of using the emerging tinymail list types.


-- 
Philip Van Hoof, software developer at x-tend 
home: me at pvanhoof dot be 
gnome: pvanhoof at gnome dot org 
work: vanhoof at x-tend dot be 
http://www.pvanhoof.be - http://www.x-tend.be