- Synch class consts with HEAD
- Synch example RecursiveTreeIterator (as far as possible)

- Add SplObjectStorage
- Add RecursiveFilterIterator
- Rename Observer to SplObserver
- Rename Subject to SplSubject
- Move SPL constants to class constants
- Update docu

  and flags now before branching for 5.1.

# update documentation
#
# In 5.2 we need to implement an event handler onException() to be invoked
# on exceptions during getChildren() calls. Its default implementation
# would simply rethrow the exception if the flag is not set and delete if
# if it was set. To do so the exceptions refcount needs to be increased
# before calling zend_clear_exception() to keep the exception alive but
# clear the control information.
#
# As a side note this is alos the easy solution to allow multi exception
# handling: Simply clear the engine's exception info and add a property
# called $previousException to the base exception and assign it from the
# already pending one.

  on the same level (while the actual child is available).