Prefer defvar-local in erc

Prefer defvar-local in erc

* lisp/erc/erc-backend.el (erc-server-current-nick)
(erc-server-process, erc-session-server, erc-session-connector)
(erc-session-port, erc-server-announced-name)
(erc-server-version, erc-server-parameters)
(erc-server-connected, erc-server-reconnect-count)
(erc-server-quitting, erc-server-reconnecting)
(erc-server-timed-out, erc-server-banned)
(erc-server-error-occurred, erc-server-lines-sent)
(erc-server-last-peers, erc-server-last-sent-time)
(erc-server-last-ping-time, erc-server-last-received-time)
(erc-server-lag, erc-server-filter-data, erc-server-duplicates)
(erc-server-processing-p, erc-server-flood-last-message)
(erc-server-flood-queue, erc-server-flood-timer)
(erc-server-ping-handler):
* lisp/erc/erc-capab.el (erc-capab-identify-activated)
(erc-capab-identify-sent):
* lisp/erc/erc-dcc.el (erc-dcc-byte-count, erc-dcc-entry-data)
(erc-dcc-file-name):
* lisp/erc/erc-ezbounce.el (erc-ezb-session-list):
* lisp/erc/erc-join.el (erc--autojoin-timer):
* lisp/erc/erc-netsplit.el (erc-netsplit-list):
* lisp/erc/erc-networks.el (erc-network):
* lisp/erc/erc-notify.el (erc-last-ison, erc-last-ison-time):
* lisp/erc/erc-ring.el (erc-input-ring, erc-input-ring-index):
* lisp/erc/erc-stamp.el (erc-timestamp-last-inserted)
(erc-timestamp-last-inserted-left)
(erc-timestamp-last-inserted-right):
* lisp/erc/erc.el (erc-session-password, erc-channel-users)
(erc-server-users, erc-channel-topic, erc-channel-modes)
(erc-insert-marker, erc-input-marker, erc-last-saved-position)
(erc-dbuf, erc-active-buffer, erc-default-recipients)
(erc-session-user-full-name, erc-channel-user-limit)
(erc-channel-key, erc-invitation, erc-channel-list)
(erc-bad-nick, erc-logged-in, erc-default-nicks)
(erc-nick-change-attempt-count, erc-send-input-line-function)
(erc-channel-new-member-names, erc-channel-banlist)
(erc-current-message-catalog): Prefer defvar-local.