* doc/lispref/backups.texi (Auto-Saving): Explain UNIQUIFY being a
secure hash in auto-save-file-name-transforms.
* etc/NEWS: Mention change in `auto-save-file-name-transforms'.
* lisp/files.el (auto-save-file-name-transforms): Adapt docstring.
(make-auto-save-file-name): Care, if UNIQ is a secure hash symbol.