message: Use TBB in viewer with Intel compiler
diff: #include <visionaray/point_light.h>
  #include <visionaray/scheduler.h>
  -#if defined(__MINGW32__) || defined(__MINGW64__)
  +#if defined(__INTEL_COMPILER) || defined(__MINGW32__) || defined(__MINGW64__)
  #include <visionaray/experimental/tbb_sched.h>
  #endif
  @@ -249,7 +249,7 @@ struct renderer : viewer_type
  thrust::device_vector<device_tex_ref_type> device_textures;
  #endif
  -#if defined(__MINGW32__) || defined(__MINGW64__)
  +#if defined(__INTEL_COMPILER) || defined(__MINGW32__) || defined(__MINGW64__)
  tbb_sched<ray_type_cpu> host_sched;
  #else
  tiled_sched<ray_type_cpu> host_sched;
  