gst/gstiterator.*: Added missing files.

gst/gstiterator.*: Added missing files.

Original commit message from CVS:
* gst/gstiterator.c: (gst_iterator_init), (gst_iterator_new),
(gst_list_iterator_next), (gst_list_iterator_resync),
(gst_list_iterator_free), (gst_iterator_new_list),
(gst_iterator_pop), (gst_iterator_next), (gst_iterator_resync),
(gst_iterator_free), (gst_iterator_push), (filter_next),
(filter_resync), (filter_uninit), (filter_free),
(gst_iterator_filter), (gst_iterator_fold), (foreach_fold_func),
(gst_iterator_foreach), (find_custom_fold_func),
(gst_iterator_find_custom):
* gst/gstiterator.h:
Added missing files.