Remove purecopy calls from files.el

Remove purecopy calls from files.el

* lisp/files.el (null-device, file-name-invalid-regexp)
(locate-dominating-stop-dir-regexp, auto-mode-alist)
(interpreter-mode-alist, inhibit-local-variables-regexps)
(auto-mode-interpreter-regexp, magic-fallback-mode-alist)
(save-some-buffers-action-alist, list-directory-brief-switches)
(list-directory-verbose-switches, insert-directory-program)
(directory-free-space-program, directory-free-space-args)
(directory-listing-before-filename-regexp)
(file-name-handler-alist): Remove all purecopy calls.

(cherry picked from commit 538a2428983c3aaf300bba920bc9f7e4d718982e)