[gtkada] Accellerator maps

[Manuel Op de Coul]

> Ada Core Technologies and ACT Europe are pleased to announce the first
> public release of GPS, the GNAT Programming System IDE, for the
> GNU/Linux, Solaris and Windows platforms.

Very impressive, you guys haven't been sitting still!

In the spec of Gtk.Menu_Item, the file gtk-accel_map.ads is
mentioned. However this package isn't provided with GtkAda.
I don't know whether it was forgotten to be included, or not yet made.

Manuel