bug#15234: 24.3.50; Make C-x u repeatable

[Juri Linkov]

>> Make C-x u repeatable.
>
> FWIW, this is what I use:
>
> (defun undo-repeat (arg)

You can make any command repeatable more easily with:

(advice-add 'undo :after
            (lambda (delta)
              (set-temporary-overlay-map
               (let ((map (make-sparse-keymap)))
                 (define-key map (vector last-command-event) this-command)
                 map))))