operator+(const nsTAString_CharT& a, const nsTAString_CharT& b)
operator+(const nsTSubstringTuple_CharT::base_string_type& a, const nsTSubstringTuple_CharT::base_string_type& b)
operator+(const nsTAString_CharT& a, const nsTAString_CharT& b)  {    return nsTSubstringTuple_CharT(&a, &b);  }