message: Portable range check for *cursor_ value.
  Avoids the following compile error when char is unsigned:
  error: comparison of unsigned expression >= 0 is always true [-Werror,-Wtautological-unsigned-zero-compare]
diff: @@ -280,7 +280,7 @@ CheckedError Parser::Next() {
  int unicode_high_surrogate = -1;
  while (*cursor_ != c) {
  - if (*cursor_ < ' ' && *cursor_ >= 0)
  + if (*cursor_ < ' ' && static_cast<signed char>(*cursor_) >= 0)
  return Error("illegal character in string constant");
  if (*cursor_ == '\\') {
  cursor_++;
  