gst/gstevent.*: Some more debugging output and doc cleanups.

gst/gstevent.*: Some more debugging output and doc cleanups.

Original commit message from CVS:
* gst/gstevent.c: (_gst_event_copy), (gst_event_new_custom),
(gst_event_new_newsegment), (gst_event_parse_newsegment),
(gst_event_new_tag), (gst_event_parse_tag), (gst_event_new_qos),
(gst_event_parse_qos), (gst_event_new_seek),
(gst_event_parse_seek):
* gst/gstevent.h:
Some more debugging output and doc cleanups.

* gst/gstqueue.c: (gst_queue_handle_sink_event):
Fix possible deadlock.