* Added xml/saxbookmarks, xml/dombookmarks and widgets/tooltips examples
* Improved garbage collection marking, Children QTreeWidgets and
QListWidgets are now marked. QObject tree instances are only marked
starting at an instance which has no parent to improved efficiency,
otherwise the same sub trees would be marked several times as a
traversal is started for each node in the heirarchy.
* The 'type' method in QEvent subclasses now works correctly.
* Added inspect and pretty_print methods to the Qt::WidgetTreeItem class