gst/gstbin.c: Some documentation updates.

gst/gstbin.c: Some documentation updates.

Original commit message from CVS:
* gst/gstbin.c: (add_to_queue), (clear_queue), (reset_outdegree),
(update_outdegree), (find_element), (gst_bin_sort_iterator_next),
(gst_bin_sort_iterator_resync), (gst_bin_sort_iterator_free),
(gst_bin_iterate_sorted), (gst_bin_element_set_state),
(gst_bin_change_state), (gst_bin_dispose):
Some documentation updates.
Clean up dispose handlers.

* gst/gstobject.c: (gst_object_ref), (gst_object_unref):
* gst/gstpad.c: (gst_pad_dispose):
Clean up dispose handler.

* gst/gstpipeline.c: (gst_pipeline_change_state):
Removed spurious UNLOCK.