(url-cookie-name, url-cookie-value, url-cookie-expires, url-cookie-localpart)

(url-cookie-name, url-cookie-value, url-cookie-expires, url-cookie-localpart)
(url-cookie-domain, url-cookie-secure, url-cookie-set-name)
(url-cookie-set-value, url-cookie-set-expires, url-cookie-set-localpart)
(url-cookie-set-domain, url-cookie-set-secure, url-cookie-retrieve-arg)
(url-cookie-create, url-cookie-p): Remove.
(url-cookie): New struct.
(url-cookie-store): Use setf instead of url-cookie-set-*.