message: Corrected unnnecessary const restriction on returned std::string
diff: @@ -2656,9 +2656,9 @@ scan_number_done:
  int get()
  {
  ++chars_read;
  - int c = current = ia->get_character();
  - token_string.push_back(static_cast<char>(c));
  - return c;
  + current = ia->get_character();
  + token_string.push_back(static_cast<char>(current));
  + return current;
  }
  /// unget current character (return it again on next get)
  @@ -2703,7 +2703,7 @@ scan_number_done:
  }
  /// return string value
  - const std::string get_string()
  + std::string get_string()
  {
  return std::move( yytext );
  }
  