Log Message:
Update sylpheed to 3.3.1.

* 3.3.1 (stable)

    * IMAP: "INBOX" folder became case insensitive as specified in RFC \ 
3501.
    * IMAP: server name for cache directory is escaped now
      (fixes cache creation when using IPv6 address for server name on Windows).
    * IMAP: the bug that double-quote (") and backslash (\) in
      folder/username/password were not escaped and could not be used on IMAP4
      was fixed.
    * IMAP: parsing of folder names that contain brackets was fixed.
    * Config.guess and config.sub included in the tarball were updated to the
      latest version.
    * The bug that 'File - Folder - Move folder...' menu didn't work was
      fixed.
    * The bug that MIME nest level restriction was not working was fixed.
    * Many defects discovered by Coverity Scan were fixed:
      - FILE handle resource leaks
      - memory leaks
      - possible buffer overrun
      - strict error checks
      - correct null pointer checks
    * Win32: the tray icon is recreated when explorer.exe crashes now.
    * Win32: the included SSL certificates were updated
      (based on ca-certificates_20111211_all.deb in Ubuntu 12.04.4 LTS).