* Do not take and release the structure lock for each element of the list while

* Do not take and release the structure lock for each element of the list while
  releasing it. mutex locks /= 20 on a standard preparse run
* Only create absolutely necessary variables while preparsing
--> Preparse speed *= 4 (with item in disk cache of course)

* Do not rebuild playlist too much while adding a directory. Add a new flag
  to NodeCreate and Add to control this behaviour