Original commit message from CVS:
* docs/design/part-TODO.txt:
* gst/gstbin.c: (gst_bin_class_init), (gst_bin_provide_clock_func),
(gst_bin_add_func), (gst_bin_remove_func), (bin_bus_handler),
(gst_bin_handle_message_func):
* gst/gstbin.h:
Make message handling overridable.