* lisp/erc/erc.el: Use lexical-binding.
(erc-user-full-name): Minor CSE simplification.
(erc-mode-map): Assume command-remapping is available.
(erc-once-with-server-event): Replace `forms' arg with a function arg.
(erc-once-with-server-event-global): Remove.
(erc-ison-p): Adjust to change in erc-once-with-server-event.
(erc-get-buffer-create): Remove arg `proc'.
(iswitchb-make-buflist-hook): Declare.
(erc-setup-buffer): Use pcase; avoid ((lambda ..) ..).
(read-passwd): Assume it exists.
(erc-display-line, erc-cmd-IDLE): Avoid add-to-list, adjust to change
in erc-once-with-server-event.
(erc-cmd-JOIN, erc-set-channel-limit, erc-set-channel-key)
(erc-add-query): Minor CSE simplification.
(erc-cmd-BANLIST, erc-cmd-MASSUNBAN): Adjust to change
in erc-once-with-server-event.
(erc-echo-notice-in-user-and-target-buffers): Avoid add-to-list.
* lisp/erc/erc-track.el: Use lexical-binding.
(erc-make-mode-line-buffer-name): Use closures instead of `(lambda...).
(erc-faces-in): Avoid add-to-list.
* lisp/erc/erc-notify.el: Use lexical-binding.
(erc-notify-timer): Adjust to change in erc-once-with-server-event.
(erc-notify-QUIT): Use a closure instead of `(lambda...).
* lisp/erc/erc-list.el: Use lexical-binding.
(erc-list-install-322-handler, erc-cmd-LIST): Adjust to change in
erc-once-with-server-event.
* lisp/erc/erc-button.el: Use lexical-binding.
(erc-button-next-function): Use a closure instead of `(lambda...).