message: gltfpack: Update KTX2 DFD to match recent spec update
  sampleUpper and channel qualifiers should match those of
  block-compressed textures when using Basis; sampleUpper is set to
  UINT32_MAX for unsigned formats. Also, when using sRGB with a 4-channel
  texture, alpha channel must specify linear qualifier explicitly.
diff: @@ -125,7 +125,12 @@ static void createDfd(std::vector<uint32_t>& result, int channels, bool srgb)
  for (int i = 0; i < channels; ++i)
  {
  + uint32_t qualifiers = (srgb && i == 3) ? KHR_DF_SAMPLE_DATATYPE_LINEAR : 0;
  +
  KHR_DFDSETSVAL(dfd, i, CHANNELID, channel_enums[i]);
  + KHR_DFDSETSVAL(dfd, i, QUALIFIERS, qualifiers);
  + KHR_DFDSETSVAL(dfd, i, SAMPLELOWER, 0);
  + KHR_DFDSETSVAL(dfd, i, SAMPLEUPPER, ~0u);
  }
  }
  