message: Enum tags: Make size field unsigned
  Underwise this overflows for e.g. 8 bit enums with more then 128 entries (Key list)
diff: @@ -22,7 +22,7 @@ template <typename E, size_t N>
  class EnumTags {
  public:
  static constexpr size_t num_tags = N;
  - using int_type = typename std::make_signed<typename std::underlying_type<E>::type>::type;
  + using int_type = typename std::make_unsigned<typename std::underlying_type<E>::type>::type;
  using iterator = char const * const *;
  using reverse_iterator = std::reverse_iterator<iterator>;
  