gst/matroska/matroska-demux.c: Improve debug output everywhere and fix the EOS logic.

gst/matroska/matroska-demux.c: Improve debug output everywhere and fix the EOS logic.

Original commit message from CVS:
* gst/matroska/matroska-demux.c: (gst_matroska_demux_reset),
(gst_matroska_demux_stream_from_num),
(gst_matroska_demux_encoding_cmp),
(gst_matroska_demux_encoding_order_unique),
(gst_matroska_demux_read_track_encoding),
(gst_matroska_demux_read_track_encodings),
(gst_matroska_demux_tracknumber_unique),
(gst_matroska_demux_add_stream), (gst_matroska_demux_init_stream),
(gst_matroska_demux_parse_tracks),
(gst_matroska_demux_parse_index_cuetrack),
(gst_matroska_demux_parse_index_pointentry),
(gst_matroska_demux_parse_index), (gst_matroska_demux_parse_info),
(gst_matroska_demux_parse_metadata_id_simple_tag),
(gst_matroska_demux_parse_metadata_id_tag),
(gst_matroska_demux_parse_metadata),
(gst_matroska_demux_parse_attached_file),
(gst_matroska_demux_parse_attachments),
(gst_matroska_demux_parse_chapters),
(gst_matroska_demux_sync_streams), (gst_matroska_decode_buffer),
(gst_matroska_demux_parse_blockgroup_or_simpleblock),
(gst_matroska_demux_parse_cluster),
(gst_matroska_demux_parse_contents_seekentry),
(gst_matroska_demux_parse_contents),
(gst_matroska_demux_loop_stream_parse_id),
(gst_matroska_demux_loop):
Improve debug output everywhere and fix the EOS logic.
Check the values of the ContentEncoding elements more strictly and
don't use tracks for which it's invalid.
Check that the track number is unique for this stream.
Check that seek positions are below G_MAXINT64 as our seeks are
int64-based and overflows will fail badly.
After seeks also don't push SimpleBlocks until the first one
containing a keyframe is found. Before this was done only for normal
Blocks.
Update some FIXME/TODOs.
* gst/matroska/ebml-read.c: (gst_ebml_read_peek_bytes),
(gst_ebml_read_utf8), (gst_ebml_read_header):
Improve debug output.
* gst/matroska/matroska-ids.c:
(gst_matroska_track_init_video_context):
* gst/matroska/matroska-ids.h:
* gst/matroska/matroska-mux.c:
(gst_matroska_mux_video_pad_setcaps):
Remove eye mode and don't parse it anymore. We can't use that
information in GStreamer yet so it's useless.