fix rate helpers to run with current SWIG
fix rate helpers to run with current SWIG


fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG,fabrice-lecuyer/QuantLib-SWIG