gst/: Protect flags with proper lock. unref provided cached clock in dispose.

gst/: Protect flags with proper lock. unref provided cached clock in dispose.

Original commit message from CVS:
* gst/gstbin.c: (gst_bin_add_func), (gst_bin_remove_func),
(reset_degree), (gst_bin_dispose), (bin_bus_handler):
* gst/gstelement.c: (gst_element_commit_state),
(gst_element_set_state):
Protect flags with proper lock.
unref provided cached clock in dispose.