* Put ErrorThread() in input_ext-dec.h because it was the same function

  * Put ErrorThread() in input_ext-dec.h because it was the same function
    in all decoders. Called it DecoderError() instead.
  * All decoders enter DecoderError() in case of error, even if they
    haven't allocated all their data. This prevents the input from getting
    stuck if a decoder has failed its initialization.
  * Namespace fixes through the decoder files.