gst/audiorate/gstaudiorate.c: Keep sink and src segment to keep track of time and support more input formats.

Original commit message from CVS:
* gst/audiorate/gstaudiorate.c: (gst_audio_rate_reset),
(gst_audio_rate_sink_event), (gst_audio_rate_convert),
(gst_audio_rate_convert_segments), (gst_audio_rate_chain):
Keep sink and src segment to keep track of time and support more
input formats.
Fix bogus next_offset and run_time calculation, don't understand how
this could have worked before. Fixes #357976.
Remove some unneeded vars.