ext/speex/gstspeexenc.c: Add mode property.

ext/speex/gstspeexenc.c: Add mode property.

Original commit message from CVS:
* ext/speex/gstspeexenc.c: (gst_speex_enc_mode_get_type),
(gst_speex_enc_class_init), (gst_speex_enc_sink_getcaps),
(gst_speex_enc_get_latency), (gst_speex_enc_get_query_types),
(gst_speex_enc_src_query), (gst_speex_enc_init),
(gst_speex_enc_setup), (gst_speex_enc_push_buffer),
(gst_speex_enc_chain), (gst_speex_enc_get_property),
(gst_speex_enc_set_property):
Add mode property.
Some cleanups, add more debug info.
Add latency query.