Use lexical-binding in all of `lisp/url`

Use lexical-binding in all of `lisp/url`

* lisp/url/url-dav.el: Use lexical-binding.
(url-dav-process-DAV:prop): Remove unused var `handler-func`.
(url-dav-lock-resource): Remove unused var `child-url`.
(url-dav-active-locks): Remove unused var `properties`.
(url-dav-delete-directory): Remove unused var `props`.
(url-dav-file-name-completion): Remove unused var `result`.

* lisp/url/url-expand.el (url-expand-file-name): Use \s

* lisp/url/url-file.el (url-file): Improve regexp.

* lisp/url/url-gw.el: Use lexical-binding.
(url-open-stream): Remove unused var `cur-retries`, `retry`, `errobj`.

* lisp/url/url-imap.el: Use lexical-binding.
(imap-username, imap-password): Declare.

* lisp/url/url-mailto.el: Use lexical-binding.
(url-mailto): Remove unused var `func`.  Use `push`.

* lisp/url/url-news.el: Use lexical-binding.
(url-news): Remove unused var `article-brackets`.

* lisp/url/url-cid.el:
* lisp/url/url-cache.el:
* lisp/url/url-about.el:
* lisp/url/url-tramp.el:
* lisp/url/url-proxy.el:
* lisp/url/url-privacy.el:
* lisp/url/url-nfs.el:
* lisp/url/url-ldap.el:
* lisp/url/url-misc.el:
* lisp/url/url-methods.el: Use lexical-binding.