* elmo-util.el (elmo-collect-separators): New function.

* elmo-util.el (elmo-collect-separators): New function.
(elmo-collect-separators-internal): Ditto.
(elmo-collect-trail-separators): Ditto.
(elmo-parse-separated-tokens): Ditto.
(elmo-parse-separated-tokens-internal): Ditto.
(elmo-quote-syntactical-element): Ditto.

* elmo-pop3.el (elmo-pop3-folder-name-syntax): New constant.
(elmo-folder-initialize): Rewrite by `elmo-parse-separated-tokens'.

* elmo-nntp.el (elmo-nntp-folder-name-syntax): New constant.
(elmo-folder-initialize): Rewrite by `elmo-parse-separated-tokens'.
(elmo-nntp-folder-list-subfolders): Quote a user name.

* elmo-net.el (elmo-net-folder-name-syntax): New constant.
(elmo-net-parse-network): Abolish.
(elmo-net-folder-set-parameters): New function.
(elmo-folder-initialize): Follow the above change.

* elmo-imap4.el (elmo-imap4-folder-name-syntax): New constant.
(elmo-folder-initialize): Rewrite by `elmo-parse-separated-tokens'.
(elmo-folder-list-subfolders): Use
`elmo-quote-syntactical-element' instead of
`elmo-net-format-quoted' to quote mailbox and user name.