gtk_window_set_default/set_focus()

[Owen Taylor <otaylor redhat com>]

Noticed that we hadn't made these internal functions _prefixed
and also noticed that in an LXR search, they are being used
quite a bit. (Especially gtk_window_set_focus())

We can't simply deprecate them and _prefix later, because
they don't work the same as the proper 
gtk_widget_grab_focus() gtk_widget_grab_default().

We could:

 - Make gtk_window_set_focus() call gtk_widget_grab_focus()
   then make gtk_widget_grab_focus() call 
   _gtk_widget_really_grab_focus().

But it might be better to:

 - But IMO, we should just _prefix them immediately and let
   people fix their code.

One thing to note is that if you actually want to _unset_
the focus in a window (should this even be allowed?) 
gtk_window_set_focus (window, NULL); is the only way
to do this.

Opinions?
                                        Owen