sys/oss/gstosssink.c: Latest fixes for A/V sync, audio playback and such. This is about all... MPEG playback issues a...

Original commit message from CVS:
* sys/oss/gstosssink.c: (gst_osssink_init), (gst_osssink_get_time),
(gst_osssink_chain), (gst_osssink_change_state):
Latest fixes for A/V sync, audio playback and such. This is about
all... MPEG playback issues are mostly related to the async build-
up of MPEG files, I cannot fix that. Use basicgthread to solve it.