message: Fixed Uint() method actually storing a signed int.
  Also fixed two constructors missing explicit.
diff: @@ -879,7 +879,7 @@ class Builder FLATBUFFERS_FINAL_CLASS {
  void UInt(uint64_t u) { stack_.push_back(Value(u, FBT_UINT, WidthU(u))); }
  void UInt(const char *key, uint64_t u) {
  Key(key);
  - Int(u);
  + UInt(u);
  }
  void Float(float f) { stack_.push_back(Value(f)); }
  @@ -1483,7 +1483,7 @@ class Builder FLATBUFFERS_FINAL_CLASS {
  BitWidth force_min_bit_width_;
  struct KeyOffsetCompare {
  - KeyOffsetCompare(const std::vector<uint8_t> &buf) : buf_(&buf) {}
  + explicit KeyOffsetCompare(const std::vector<uint8_t> &buf) : buf_(&buf) {}
  bool operator()(size_t a, size_t b) const {
  auto stra =
  reinterpret_cast<const char *>(flatbuffers::vector_data(*buf_) + a);
  @@ -1496,7 +1496,7 @@ class Builder FLATBUFFERS_FINAL_CLASS {
  typedef std::pair<size_t, size_t> StringOffset;
  struct StringOffsetCompare {
  - StringOffsetCompare(const std::vector<uint8_t> &buf) : buf_(&buf) {}
  + explicit StringOffsetCompare(const std::vector<uint8_t> &buf) : buf_(&buf) {}
  bool operator()(const StringOffset &a, const StringOffset &b) const {
  auto stra = reinterpret_cast<const char *>(
  flatbuffers::vector_data(*buf_) + a.first);
  