plugins/ogg: Refactor to conquer

plugins/ogg: Refactor to conquer

  * Add reference links
  * Parse all streams in a file - we only consider the first one
    regarding audio files, but this paves the way to support video
    (which has never been supported in ogg plugin)
  * Split the file parsing into pages/packets/codec-data. This makes it
    easier to support theora (needed for video) and also for removing
    libvorbis if it's desired in the future
  * Be safer regarding packets crossing page boundaries
  * Be safer regarding EOF in the middle of parsing