gst/base/gstbasesink.c: Reworked the base sink, handle event and buffer serialisation...

gst/base/gstbasesink.c: Reworked the base sink, handle event and buffer serialisation correctly and removed possible ...

Original commit message from CVS:
* gst/base/gstbasesink.c: (gst_basesink_set_property),
(gst_basesink_preroll_queue_empty),
(gst_basesink_preroll_queue_flush), (gst_basesink_handle_object),
(gst_basesink_event), (gst_basesink_do_sync),
(gst_basesink_handle_event), (gst_basesink_handle_buffer),
(gst_basesink_chain), (gst_basesink_loop), (gst_basesink_activate),
(gst_basesink_change_state):
Reworked the base sink, handle event and buffer serialisation
correctly and removed possible deadlock.
Handle EOS correctly.