Support kate subtitles in ogg

[Carl Eugen Hoyos]

​http://streams.videolan.org/streams/ogg/kiki_Theora_Vorbis_kate.ogg
The sample shows subtitles with vlc that are not detected with current FFmpeg.

$ ffmpeg -i kiki_Theora_Vorbis_kate.ogg
ffmpeg version N-56984-gf115e83 Copyright (c) 2000-2013 the FFmpeg developers
  built on Oct  9 2013 08:55:45 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --enable-version3 --enable-libvo-aacenc
  libavutil      52. 46.101 / 52. 46.101
  libavcodec     55. 35.100 / 55. 35.100
  libavformat    55. 19.100 / 55. 19.100
  libavdevice    55.  4.100 / 55.  4.100
  libavfilter     3. 88.101 /  3. 88.101
  libswscale      2.  5.101 /  2.  5.101
  libswresample   0. 17.103 /  0. 17.103
  libpostproc    52.  3.100 / 52.  3.100
[ogg @ 0x23f8080] Codec not found
    Last message repeated 1 times
[theora @ 0x23f9760] 7 bits left in packet 82
[ogg @ 0x23f8080] Broken file, keyframe not correctly marked.
[ogg @ 0x23f8080] Could not find codec parameters for stream 2 (Unknown: none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
[ogg @ 0x23f8080] Could not find codec parameters for stream 3 (Unknown: none): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, ogg, from 'kiki_Theora_Vorbis_kate.ogg':
  Duration: 00:00:46.23, start: 0.000000, bitrate: 2251 kb/s
    Stream #0:0: Data: none
    Stream #0:1: Video: theora, yuv420p, 544x432 [SAR 64:45 DAR 2176:1215], 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:2: Unknown: none
    Stream #0:3: Unknown: none
    Stream #0:4(ja): Audio: vorbis, 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      TITLE           : Title 5 - Main Feature
      COMMENT         : Created with thoggen: http://thoggen.net
      LANGUAGE        : ja
    Stream #0:5(en): Audio: vorbis, 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      TITLE           : Title 5 - Main Feature
      COMMENT         : Created with thoggen: http://thoggen.net
      LANGUAGE        : en
At least one output file must be specified

[sebma]

I also created an ogv file thanks to this documentation : ​Ogg Theora Cook Book - Embedding Subtitles but ffmpeg version 4.4.1-static still does not recognize kate subtitles.