message: Fix an type error, should input chars not numbers
diff: @@ -608,7 +608,7 @@ struct BenchmarkQueryInsensitiveString : BenchmarkWithStringsTable {
  for (size_t c = 0; c < length; ++c) {
  bool lowercase = (rand() % 2) == 0;
  // choose characters from a-z or A-Z
  - ss << (rand() % 26) + (lowercase ? 97 : 65);
  + ss << char((rand() % 26) + (lowercase ? 97 : 65));
  }
  return ss.str();
  }
  