gst/gstbin.c: Small doc fixes. get_clock -> provide_clock.

gst/gstbin.c: Small doc fixes. get_clock -> provide_clock.

Original commit message from CVS:
* gst/gstbin.c: (gst_bin_class_init), (gst_bin_provide_clock_func),
(add_to_queue), (clear_queue), (reset_degree), (update_degree),
(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):
Small doc fixes. get_clock -> provide_clock.

* gst/gstelement.c: (gst_element_class_init),
(gst_element_provides_clock), (gst_element_provide_clock),
(gst_element_get_clock), (gst_element_commit_state),
(gst_element_lost_state):
* gst/gstelement.h:
Make get/set_clock() symetric. Add provide_clock vmethod since
that is actually what this function does.

* gst/gstpipeline.c: (gst_pipeline_class_init),
(gst_pipeline_change_state), (gst_pipeline_provide_clock_func),
(gst_pipeline_get_clock):
get_clock -> provide_clock.