ext/speex/gstspeexdec.c: Make metadata extraction actually work.

ext/speex/gstspeexdec.c: Make metadata extraction actually work.

Original commit message from CVS:
* ext/speex/gstspeexdec.c: (speex_dec_chain_parse_comments):
Make metadata extraction actually work.
* ext/speex/gstspeexenc.c: (gst_speexenc_base_init),
(gst_speexenc_init), (gst_speexenc_create_metadata_buffer),
(gst_speexenc_chain):
Fix metadata writing: replace old code which wrote completely
broken tags with libgsttag-based code. Plus miscellaneous
code cleanups (use static pad templates etc.) and a bunch
of leak fixes.