Update imp to 4.0.4

Update imp to 4.0.4
From the ChangeLog:
> IMP, the Internet Messaging Program, is one of the most popular webmail
> applications available.  It allows universal, web-based access to IMAP and
> POP3 mail servers and provides a full range of features normally found only in
> desktop email clients.
>
> Major changes compared to the IMP version H3 (4.0.4-RC2) are:
>     * Added warning that PGP key generation may take awhile.
>     * Added confirmation when reporting spam/innocent from message view.
>     * Fixed check for duplicate addresses when automatically saving recipients.
>     * Updated Finnish, German, Korean, and Slovak translations.
>
> Major changes compared to the IMP version H3 (4.0.4-RC1) are:
>     * Added entire message search to search page.
>     * Use "Fetch Mail" consistently in the user interface.
>     * Fixed warnings when expanding names with spaces.
>     * Updated Finnish, German, Korean, and Slovak translations.
>     * Minor bug fixes.
>
> Major changes compared to the IMP version H3 (4.0.3) are:
>     * Allow non-ascii searches.
>     * Show meeting invitations inline.
>     * Allow to accept invitations and add them to the calendar at once.
>     * Added separate confirmation page when deleting or emptying folders.
>     * Localized all remaining INBOX strings in the interface.
>     * Ensure that no maintenance tasks may be skipped.
>     * Fixed blank screens in Internet Explorer after failed logins.
>     * Minor character set related fixes.
>     * Improved draft saving of HTML messages.
>     * Work around broken c-client sort by arrival.
>     * Added Bosnian translation.
>     * A few improvements and minor bug fixes.