message: fix s3tc compression with HDR input
  HDR input where producing garbage pixels, instead we saturate.
diff: @@ -366,10 +366,10 @@ static void extract4x4RGBA(uint8_t* dst, const LinearImage& source, uint32_t x0,
  int clamped_x = imin(maxx, x);
  int clamped_y = imin(maxy, y);
  float const* rgba = source.getPixelRef(clamped_x, clamped_y);
  - dst[0] = (uint8_t) (rgba[0] * 255.0f);
  - dst[1] = (uint8_t) (rgba[1] * 255.0f);
  - dst[2] = (uint8_t) (rgba[2] * 255.0f);
  - dst[3] = (uint8_t) (rgba[3] * 255.0f);
  + dst[0] = (uint8_t) std::min(255.0f, std::max(0.0f, (rgba[0] * 255.0f)));
  + dst[1] = (uint8_t) std::min(255.0f, std::max(0.0f, (rgba[1] * 255.0f)));
  + dst[2] = (uint8_t) std::min(255.0f, std::max(0.0f, (rgba[2] * 255.0f)));
  + dst[3] = (uint8_t) std::min(255.0f, std::max(0.0f, (rgba[3] * 255.0f)));
  }
  }
  }
  