popup menu created from menu model has accelerators shown
Submitted by Christian Persch
When using gtk_menu_new_from_model() to create e.g. a context menu, the resulting menu shows accelerators, which is unusual and unwanted for context menus. It didn't see a way to disable these. GtkUIManager OTOH defaulted to not showing accelerators for popup menus, and provided an explicit way to show them when desired, which is the unusual case.