gst/matroska/: Handle EBML elements like Void or CRC32 in the EbmlRead base class already. They're not useful in the ...

Original commit message from CVS:
* gst/matroska/ebml-read.c: (gst_ebml_peek_id),
(gst_ebml_read_header):
* gst/matroska/matroska-demux.c: (gst_matroska_demux_add_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_attachments),
(gst_matroska_demux_parse_chapters),
(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):
Handle EBML elements like Void or CRC32 in the EbmlRead base class
already. They're not useful in the matroska parser and only cause
additional code.