message: Missing include, and code layout
diff: #pragma once
  #ifndef VSNRAY_SPECTRUM_H
  -#define VSNRAY_SPECTRUM_H
  +#define VSNRAY_SPECTRUM_H 1
  -#include <visionaray/detail/macros.h>
  -#include <visionaray/math/vector.h>
  +#include <cstddef>
  +
  +#include "detail/macros.h"
  +#include "math/vector.h"
  //-------------------------------------------------------------------------------------------------
  