* lisp/erc/erc-track.el, lisp/erc/erc-networks.el, lisp/erc/erc-netsplit.el:
* lisp/erc/erc-dcc.el, lisp/erc/erc-backend.el: Use cl-lib, nth, pcase, and
called-interactively-p instead of cl.
* lisp/erc/erc-speedbar.el, lisp/erc/erc-services.el:
* lisp/erc/erc-pcomplete.el, lisp/erc/erc-notify.el, lisp/erc/erc-match.el:
* lisp/erc/erc-log.el, lisp/erc/erc-join.el, lisp/erc/erc-ezbounce.el:
* lisp/erc/erc-capab.el: Don't require cl since we don't use it.
* lisp/erc/erc.el: Use cl-lib, nth, pcase, and called-interactively-p i.s.o cl.
(erc-lurker-ignore-chars, erc-common-server-suffixes): Move before first use.
* lisp/json.el: Don't require cl since we don't use it.
* lisp/color.el: Don't require cl.
(color-complement): `caddr' -> `nth 2'.
* test/automated/ert-x-tests.el: Use cl-lib.
* test/automated/ert-tests.el: Use lexical-binding and cl-lib.
* lisp/erc/erc-join.el (erc-server-join-channel): New function to look up
the channel password via auth-source.
(erc-autojoin-channels): Use it.
(erc-autojoin-after-ident): Ditto.
(erc-autojoin-channels-alist): Mention auth-source.
* lisp/erc/erc-backend.el (erc-coding-system-precedence):
* lisp/erc/erc-join.el (erc-autojoin-delay, erc-autojoin-timing):
Add missing :version settings.
* etc/NEWS: We don't need to duplicate the doc-strings of variables.
