ext/speex/: Fix seeking and duration queries (#337033); clean up and refactor a bit.

ext/speex/: Fix seeking and duration queries (#337033); clean up and refactor a bit.

Original commit message from CVS:
* ext/speex/gstspeex.c: (plugin_init):
* ext/speex/gstspeexdec.c: (gst_speex_dec_class_init),
(gst_speex_dec_reset), (gst_speex_dec_init), (speex_dec_convert),
(speex_get_sink_query_types), (speex_dec_sink_query),
(speex_get_src_query_types), (speex_dec_src_query),
(speex_dec_src_event), (speex_dec_sink_event),
(speex_dec_chain_parse_header), (speex_dec_chain_parse_comments),
(speex_dec_chain_parse_data), (speex_dec_chain),
(gst_speex_dec_get_property), (gst_speex_dec_set_property),
(speex_dec_change_state):
* ext/speex/gstspeexdec.h:
Fix seeking and duration queries (#337033); clean up and
refactor a bit.