Changes from 2.6.0

    * The plug-in system was implemented (still experimental. See PLUGIN.txt for detail).
    * LibSylph (internal version) is built as shared library now.
    * The update check feature was implemented (requires curl command, included in Windows installer).
    * fsync() will be called after writing configuration files.
    * 'Send queued messages' is shown instead of 'Mark all read' in the context menu of the Queue folder.
    * The default command line options of spam filters were modified.
    * Win32: Hard link will be used to improve file I/O performance if available.
    * Win32: bsfilter is included in the installer now. If you have installed bsfilter at another location, please note that the location of database files might change.
    * Win32: Install/uninstall will be aborted if Sylpheed is running.
    * Win32: The registration of Start menu will be applied to all users.
    * Win32: The installer cannot launch Sylpheed anymore when install finishes (for Vista).
    * A crash bug on CSV import of the address book was fixed.
    * Several other bugfixes were made.

(ahoka)