gst/gstevent.c: copy navigation event correctly. Check freeing tag lists.

gst/gstevent.c: copy navigation event correctly. Check freeing tag lists.

Original commit message from CVS:
2004-02-20  Benjamin Otte  <otte@gnome.org>

* gst/gstevent.c: (_gst_event_copy), (_gst_event_free):
copy navigation event correctly. Check freeing tag lists.
* gst/gstthread.c: (gst_thread_change_state):
don't abort() on state changing mess - it might happen because of
bugs.
* gst/gstvalue.c: (gst_value_set_caps), (gst_value_get_caps):
use boxed functions
* gst/gstvalue.h:
fix GST_VALUE_HOLDS_CAPS