- Patch #146425 by pwolanin et al:

    * Removes the hard-coded 'book' type and perform all node actions
      equally on any node type via hook_nodeapi.
    * Achieves 100% integration with the menu system.  Improves
      performance of book rendering.
    * All the algorithms have been changed to use the tree data structure
      returned by the menu system.
    * Added support for 'multiple books'.
    * Some UI improvements.

  This is a momumental patch that took 69 iterations. Although there is
  room for improvement, this is a big step forward.  Thanks for the
  persistence, pwolanin.