* wl-util.el (wl-biff-check-folders): Set `no-cache' argument of

* wl-util.el (wl-biff-check-folders): Set `no-cache' argument of
wl-folder-get-elmo-folder.
(wl-biff-check-folder): Set `biff' argument of
`wl-folder-check-one-entity'.
(wl-biff-check-folder-async): Setup `biff' slot of folder.

* wl-folder.el (wl-folder-get-elmo-folder): Added `no-cache' argument.
(wl-folder-check-one-entity): Added `biff' argument;
Setup `biff' slot of folder.

* elmo.el (luna-define-class): Added `biff' slot.

* elmo-pop3.el (elmo-pop3-debug): Split biff log.
(elmo-pop3-debug-inhibit-logging): Abolished.
(elmo-network-close-session): Eliminated needless let.
(elmo-pop3-get-session): Set prefix 'BIFF' if biff folder.
(elmo-pop3-send-command): Added `no-log' argument.
(elmo-pop3-process-filter): Use `with-current-buffer'.
(elmo-pop3-auth-user): Set `no-log' argument; Delete process
if login failure.
(elmo-pop3-auth-apop): Likewise.
(elmo-network-authenticate-session): Likewise.

* elmo-nntp.el (elmo-nntp-get-session): Set prefix 'BIFF'
if biff folder.

* elmo-net.el (elmo-network-session-password-key): Use class symbol
string to determine protocol.
(elmo-network-session-name-prefix): Abolished.
(elmo-network-session-cache-key): Follow the change above.
(elmo-network-open-session): Ditto.

* elmo-imap4.el (elmo-imap4-send-command): Modified error message.
(elmo-imap4-get-session): Set prefix 'BIFF' if biff folder.