* elmo-util.el (elmo-quoted-specials-list): New constant.

* elmo-util.el (elmo-quoted-specials-list): New constant.
(elmo-quoted-token): New function.

* elmo-net.el (elmo-net-quote-chars-regexp): New constant.
(elmo-net-format-quoted): New function.
(elmo-net-parse-network): Ditto.
(elmo-folder-initialize): Use it.

* elmo-nntp.el (elmo-folder-initialize): Use
`elmo-net-parse-network' to parse network specification instead of
`elmo-folder-initialize#elmo-net'.

* elmo-pop3.el (elmo-folder-initialize): Ditto.

* elmo-imap4.el (elmo-folder-initialize): Ditto.
(elmo-folder-list-subfolders): Quote folder name by
`elmo-net-format-quoted'.