Common header files for GtkMenuShell to GMenuModel parser

 GTK+ module for exporting old-style menus as GMenuModels.
 .
 Many applications implement menus as GtkMenuShells and GtkMenuItems and
 aren't looking to migrate to the newer GMenuModel API.
 .
 The AppMenu GTK+ module watches for these types of menus and exports the
 appropriate GMenuModel implementation.
 .
 This package contains header files that the GTK+2.0 and GTK+3.0 builds
 have in common.