Allison Karlitskaya authored May 08, 2013 and Jasper St. Pierre committed May 13, 2013

Add a new class, GtkMenuTrackerItem that represents a menu item, to be
used with GtkMenuTracker.

GtkMenuTracker's insert callback now works in terms of this new type
(instead of passing reference to the model and an index to the item).

GtkMenuShell now handles all of the binding tasks internally, mostly
through the use of property bindings.  Having bindings for the label and
visibility attributes, in partiular, will help with supporting upcoming
extensions to GMenuModel.

GtkModelMenu has been reduced to a helper class that has nothing to do
with GMenuModel.  It represents something closer to an "ideal" API for
GtkMenuItem if we didn't have compatibility concerns (eg: not emitting
"activate" when setting toggle state, no separate subclasses per menu
item type, supporting icons, etc.) Improvements to GtkMenuItem could
eventually shrink the size of this class or remove the need for it
entirely.

Some GtkActionHelper functionality has been duplicated in
GtkMenuTracker, which is subop...