not called.
#Merge to 5.3 pending (slight BC break on AppendIterator, as it's no
#longer possible to defer the call to the parent constructor until
#after the constructor is performed).
#Bugs fixed in an atypical way for SPL. The parent constructor call
#check is performed at construction time by using a wrapper constructor
#instead of a check on the beginning of each instance method.
#Perhaps this should be uniformized in trunk; this method was mainly
#applied only to the ones crashing, except a few iterators (at least
#AppendIterator and RecursiveIteratorIterator).
