* lisp/allout*.el: Use lexical-binding

* lisp/allout*.el: Use lexical-binding

* lisp/allout.el: Activate lexical-binding.
(allout-setup-menubar): Delete "complex no-op" function.
(allout-mode): Delete call to it.
(allout-hotspot-key-handler): Delete XEmacs-only code.
(allout-copy-exposed-to-buffer): Remove always-nil var `start-list`.

* lisp/allout-widgets.el: Activate lexical-binding.
(allout-item-icon-keymap): Use `ignore`.
(allout-widgets-exposure-change-processor): Use `cl-callf` instead of
relying on dynamic binding to apply some code to two different variables.