message: Gcc's below 7.1 return double from std::abs
  Sigh.
diff: @@ -85,7 +85,7 @@ float get_interpolator_perturbation(int16_t a1,int level)
  {
  buildErrorTable();
  if ( a1 )
  - return (2 * (a1 >= 0) - 1) * s_coding_sequence[std::abs(a1)]*(1<<level);
  + return (2 * (a1 >= 0) - 1) * s_coding_sequence[int(std::abs(a1))]*(1<<level);
  return 0.0f;
  }
  