Prefer defvar-local in allout

Prefer defvar-local in allout

* lisp/allout.el (allout-just-did-undo, allout-mode)
(allout-layout, allout-regexp, allout-bullets-string)
(allout-bullets-string-len, allout-depth-specific-regexp)
(allout-depth-one-regexp, allout-line-boundary-regexp)
(allout-bob-regexp, allout-header-subtraction)
(allout-plain-bullets-string-len, allout-mode-prior-settings)
(allout-outside-normal-auto-fill-function)
(allout-encryption-plaintext-sanitization-regexps)
(allout-encryption-ciphertext-rejection-regexps)
(allout-explicitly-deactivated, allout-recent-prefix-beginning)
(allout-recent-prefix-end, allout-recent-depth)
(allout-recent-end-of-subtree, allout-post-goto-bullet)
(allout-command-counter, allout-this-command-hid-text):
* lisp/allout-widgets.el (allout-widgets-mode)
(allout-widgets-tally, allout-widgets-mode-inhibit)
(allout-inhibit-body-modification-hook)
(allout-widgets-changes-record)
(allout-widgets-undo-exposure-record)
(allout-escaped-prefix-regexp, allout-item-icon-keymap)
(allout-item-body-keymap, allout-cue-span-keymap)
(allout-widgets-last-decoration-timing)
(allout-container-item-widget): Prefer defvar-local.