Allow the user to bind more than one keycode to a keysym for Ob Menus/Move/Resize

Allow the user to bind more than one keycode to a keysym for Ob Menus/Move/Resize

If the user has escape bound to more than one keycode then they can use any of
them to close a menu.  This change applies to the hardcoded keys in openbox,
which are used for the menus and for move/resize, and maybe other places.