bug#24073: 24.5; outline-on-heading-p sees any invisible text property as outline invisible

[Paul Rankin]

I've added the following into my major mode to patch outline until the
bug is addressed...

    (with-eval-after-load 'outline
      (advice-add 'outline-invisible-p :filter-return
                  (lambda (return) (eq return (or 'outline t)))
                  '((name . "fountain-mode-patch")))
      (dolist (fun '(outline-back-to-heading
                     outline-on-heading-p
                     outline-next-visible-heading))
        (let ((source (find-function-noselect fun)))
          (with-current-buffer (car source)
            (goto-char (cdr source))
            (eval (read (current-buffer))))))
      (message "Function `outline-invisible-p' has been patched"))

But I'm a bit concerned if users install Emacs without uncompiled Lisp
source, will this result in an error that Emacs simply can't find the
library outline?