The before and after strings matched. The only difference seems to be N_() and _(), which seems like an improvement if I correctly understood the documentation (something about not needing to call gettext() manually).
Ignore me, I mistook the #define and the stock_items. I guess this removes the stock images? It does at least match the "Add" button.
The GtkStock API is deprecated and by default it doesn't even show the icons in buttons, menus, etc. So all we're really doing here is removing it from our code since it's already removed from the default user experience and isn't really the way they expect Gtk Applications to work any more (for better or worse).