Log Message:
Update sylpheed to 0.9.12.

Note that the cache version change may lose message flags.
However the issue fixed probably does effect NetBSD, as well as FreeBSD.

Main changes are:
    * A session timeout for POP3/SMTP has been implemented.
    * The 'Print' menu on the context menu has been restored.
    * The value of CACHE_VERSION has been increased to prevent a cache
      incompatibility problem on some platforms such as FreeBSD.