gst/gstbin.*: Prepare to make current EOS message queue more generic.

gst/gstbin.*: Prepare to make current EOS message queue more generic.

Original commit message from CVS:
* gst/gstbin.c: (gst_bin_init), (gst_bin_provide_clock_func),
(is_eos), (gst_bin_add_func), (gst_bin_remove_func),
(gst_bin_recalc_state), (gst_bin_change_state_func),
(gst_bin_dispose), (bin_bus_handler):
* gst/gstbin.h:
Prepare to make current EOS message queue more generic.
Fix some typos.

* gst/gstevent.c: (gst_event_new_newsegment),
(gst_event_parse_newsegment):
* gst/gstevent.h:
Rename base to stream_time.

* gst/gstmessage.h:
Fix typo in docs.