gst/matroska/ebml-write.c: Use GDOUBLE_TO_BE() instead of (probably slower) custom...

gst/matroska/ebml-write.c: Use GDOUBLE_TO_BE() instead of (probably slower) custom code.

Original commit message from CVS:
* gst/matroska/ebml-write.c: (gst_ebml_write_float):
Use GDOUBLE_TO_BE() instead of (probably slower) custom code.
* gst/matroska/matroska-demux.c: (gst_matroska_demux_base_init),
(gst_matroska_demux_class_init), (gst_matroska_demux_init),
(gst_matroska_track_free), (gst_matroska_demux_encoding_cmp),
(gst_matroska_demux_read_track_encodings),
(gst_matroska_demux_add_stream),
(gst_matroska_demux_handle_src_query),
(gst_matroska_demux_init_stream),
(gst_matroska_demux_parse_index_cuetrack),
(gst_matroska_demux_parse_index_pointentry),
(gst_matroska_demux_parse_info),
(gst_matroska_demux_parse_metadata_id_simple_tag),
(gst_matroska_demux_parse_metadata),
(gst_matroska_demux_add_wvpk_header), (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_loop_stream_parse_id),
(gst_matroska_demux_loop), (gst_matroska_demux_video_caps),
(gst_matroska_demux_audio_caps),
(gst_matroska_demux_subtitle_caps):
* gst/matroska/matroska-demux.h:
* gst/matroska/matroska-ids.c:
(gst_matroska_track_init_subtitle_context):
* gst/matroska/matroska-ids.h:
* gst/matroska/matroska-mux.c: (gst_matroska_mux_base_init),
(gst_matroska_mux_class_init), (gst_matroska_mux_init),
(gst_matroska_mux_create_uid), (gst_matroska_mux_reset),
(gst_matroska_mux_video_pad_setcaps),
(gst_matroska_mux_audio_pad_setcaps),
(gst_matroska_mux_subtitle_pad_setcaps),
(gst_matroska_mux_request_new_pad),
(gst_matroska_mux_track_header), (gst_matroska_mux_start),
(gst_matroska_mux_write_simple_tag), (gst_matroska_mux_finish),
(gst_matroska_mux_write_data), (gst_matroska_mux_collected),
(gst_matroska_mux_set_property):
Add many FIXMEs/TODOs all over the matroska muxer and demuxer
elements, do some checks for valid values in the demuxer, handle
tracktimecodescale in the demuxer, set correct default values for all
settings in the demuxer, review and add all missing matroska
IDs and some more raw YUV formats, and some trivial cleanup.