Make the State button in Custom use extended menus

Make the State button in Custom use extended menus

* lisp/cus-edit.el (custom-actioned-widget): New variable.
Dynamically hold the widget for which to show the menu.
(custom-variable-extended-menu, custom-face-extended-menu)
(custom-group-extended-menu): Keymap menus for the State menu.  Use
custom-actioned-widget for the :enable and :selected forms.  Make
related items radio buttons.  (Bug#4787)
(custom-variable-menu, custom-face-menu, custom-group-menu): Keep for
backward compatibility, but default to nil, so we prefer the keymap
menus instead.
(custom-variable-action, custom-face-action, custom-group-action):
Pass the keymap menu to widget-choose when the simplified menus
are nil.