make-text-button no longer modifies its string arg
* etc/NEWS: Mention this. * lisp/apropos.el (apropos-library-button): * lisp/ibuf-ext.el (ibuffer-old-saved-filters-warning): There’s no longer a need copy make-text-button’s string arg. * lisp/button.el (make-text-button): Return a copy of a string arg. Delay making the copy until after error-checking.