message: COMP: fix future backward incompatibilty of ITK_MAX_THREADS
diff: #include <cmath>
  #include <vector>
  +#if ITK_VERSION_MAJOR>4 && defined ( ITK_FUTURE_LEGACY_REMOVE )
  + using itk::ITK_MAX_THREADS;
  +#endif
  +
  namespace rtk
  {
  namespace Functor
  