Log Message:
Update sylpheed to version 0.9.11

Changes:

    * The spring-loaded folder has been implemented for the folder view.
    * A function to filter selected messages has been added.
    * Always move messages by default when using DnD (copy if Ctrl key
      is pressed).
    * On filtering, the matching algorithm of 'not contain' flag has
      been fixed.
    * NNTP servers that require authentication at the beginning of the
      session has been supported.
    * The method of updating the progress dialog has been modified.
    * The context menu on the summary view has been cleaned up.
    * The image viewer has been fixed.
    * The cache handling has been fixed for AMD64 and other 64-bit
      platforms.
    * The SMTP routine has been fixed to fully comply with RFC 2821.