Use lexical-binding and require cl-lib

Use lexical-binding and require cl-lib

* net/rcirc.el (rcirc, rcirc-handler-ctcp-KEEPALIVE)
(rcirc-handler-generic, rcirc-fill-paragraph)
(rcirc-format-response-string, rcirc-target-buffer)
(rcirc-last-line, rcirc-record-activity, rcirc-split-activity)
(rcirc-activity-string, rcirc-make-trees, rcirc-cmd-ctcp)
(rcirc-ctcp-sender-PING, rcirc-browse-url)
(rcirc-markup-timestamp, rcirc-markup-attributes)
(rcirc-markup-my-nick, rcirc-markup-urls)
(rcirc-markup-bright-nicks, rcirc-markup-fill)
(rcirc-check-auth-status, rcirc-handler-WALLOPS)
(rcirc-handler-JOIN, rcirc-handler-PART-or-KICK)
(rcirc-handler-PART, rcirc-handler-KICK, rcirc-handler-QUIT)
(rcirc-handler-NICK, rcirc-handler-PING, rcirc-handler-PONG)
(rcirc-handler-TOPIC, rcirc-handler-301, rcirc-handler-317)
(rcirc-handler-332, rcirc-handler-333, rcirc-handler-477)
(rcirc-handler-MODE, rcirc-handler-353, rcirc-handler-366)
(rcirc-authenticate, rcirc-handler-INVITE, rcirc-handler-ERROR)
(rcirc-handler-ctcp-VERSION, rcirc-handler-ctcp-TIME)
(rcirc-handler-CTCP-response): Fix unused arguments warnings and
use cl-lib.