* lisp/url/url-domsuf.el (url-domsuf--public-suffix-file): New
function to look for a more recent version of public_suffix_list.dat
on the system than the one that is shipped with Emacs.
(url-domsuf-parse-file): Use above new function.
* test/lisp/url/url-domsuf-tests.el
(url-domsuf--public-suffix-file): New test.