message: Specify initializers for yytest, token_string using initializer-lists
  o We can retain -Weffc++ and specify default initializers by using
  initializer lists.  The risks are low (of additional non-conformat
  compilers), because there is already one other such initialization
  used in the code-base.
diff: @@ -2833,29 +2833,30 @@ scan_number_done:
  private:
  /// input adapter
  - detail::input_adapter_t ia = nullptr;
  + detail::input_adapter_t ia { nullptr };
  /// the current character
  - int current = std::char_traits<char>::eof();
  + int current { std::char_traits<char>::eof() };
  /// the number of characters read
  - std::size_t chars_read = 0;
  + std::size_t chars_read { 0 };
  +
  /// raw input token string (for error messages)
  - std::vector<char> token_string = std::vector<char>();
  + std::vector<char> token_string { };
  /// buffer for variable-length tokens (numbers, strings)
  - std::string yytext = "";
  + std::string yytext { };
  /// a description of occurred lexer errors
  - const char* error_message = "";
  + const char* error_message { "" };
  // number values
  - number_integer_t value_integer = 0;
  - number_unsigned_t value_unsigned = 0;
  - number_float_t value_float = 0;
  + number_integer_t value_integer { 0 };
  + number_unsigned_t value_unsigned { 0 };
  + number_float_t value_float { 0 };
  /// the decimal point
  - const char decimal_point_char = '.';
  + const char decimal_point_char { '.' };
  };
  /*!
  