message: Fix warnings with LCF_DEBUG_TRACE
diff: @@ -181,7 +181,7 @@ struct Primitive<std::vector<T>> {
  typename std::vector<T>::iterator it;
  printf(" ");
  for (it = ref.begin(); it != ref.end(); ++it) {
  - printf("%d, ", *it);
  + printf("%d, ", static_cast<int>(*it));
  }
  printf("\n");
  #endif
  