With the older libgtk+2-2.12.12-alt0.M41.4 (from Branch 4.1) or with libgtk+2-2.16.6-alt1 (from Branch 5.1), emacs22-X11-gtk-22.2-alt5 (from Branch 4.1) works well: it correctly shows "additional" menus -- added by modes invoked, as, for example, after you open a directory (C-x C-f), thedired mode is loaded, and it adds several menus, e.g., "Immediate". So, with the older libgtk+2, the "Immediate" menu has items shown in it.

But with the newer 2.20.0-alt3 (or libgtk+2-2.18.9-alt1 as well), the added menu (for example, "Immediate" by the dired mode) are shown empty.

This could be some intentional backward incompatibility of the newer libgtk+2 (then, probably, the soname should be changed) or a bug in the newer libgtk+2.