Bug#830889: Looks like my patch violates RFC3501

[Nye Liu]

 From 6.3.10:

"the STATUS command SHOULD NOT be used on the currently selected  mailbox."

but in theory, the use of STATUS to ask if new mail has arrived is also 
not legal:

"The STATUS command MUST NOT be used as a "check for new
  messages in the selected mailbox" operation (refer to
  sections 7, 7.3.1, and 7.3.2 for more information about
  the proper method for new message checking)."

6.3.10. STATUS Command

    Arguments:  mailbox name
                status data item names

    Responses:  untagged responses: STATUS

    Result:     OK - status completed
                NO - status failure: no status for that name
                BAD - command unknown or arguments invalid

       The STATUS command requests the status of the indicated mailbox.
       It does not change the currently selected mailbox, nor does it
       affect the state of any messages in the queried mailbox (in
       particular, STATUS MUST NOT cause messages to lose the \Recent
       flag).

       The STATUS command provides an alternative to opening a second
       IMAP4rev1 connection and doing an EXAMINE command on a mailbox to
       query that mailbox's status without deselecting the current
       mailbox in the first IMAP4rev1 connection.

       Unlike the LIST command, the STATUS command is not guaranteed to
       be fast in its response.  Under certain circumstances, it can be
       quite slow.  In some implementations, the server is obliged to
       open the mailbox read-only internally to obtain certain status
       information.  Also unlike the LIST command, the STATUS command
       does not accept wildcards.

            Note: The STATUS command is intended to access the
            status of mailboxes other than the currently selected
            mailbox.  Because the STATUS command can cause the
            mailbox to be opened internally, and because this
            information is available by other means on the selected
            mailbox, the STATUS command SHOULD NOT be used on the
            currently selected mailbox.

            The STATUS command MUST NOT be used as a "check for new
            messages in the selected mailbox" operation (refer to
            sections 7, 7.3.1, and 7.3.2 for more information about
            the proper method for new message checking).

            Because the STATUS command is not guaranteed to be fast
            in its results, clients SHOULD NOT expect to be able to
            issue many consecutive STATUS commands and obtain
            reasonable performance.