Export private _gtk_menu_shell_activate() to encapsulate cut-and-paste

Export private _gtk_menu_shell_activate() to encapsulate cut-and-paste

Sat Apr  6 06:57:00 2002  Owen Taylor  <otaylor@redhat.com>

        * gtk/gtkmenushell.[ch] gtk/gtkmenuitem.c: Export
        private _gtk_menu_shell_activate() to encapsulate
        cut-and-paste code.

        * gtk/gtkmenubar.c: Select the first item on the menu bar
        for F10 rather than acting as if the user pressed <Alt>F
        to select the file manager.