Unused variables when param is DIRECTION_OUT

[Paul Grinberg]

My c++ library method signature looks like this

    status_enum get(const std::string &name, std::string &ret_val);

I wrapped in my the following PyBindGen code

    mod.add_method('get',
                   ReturnValue.new('status_enum'),
                   [
                       Parameter.new('const std::string&', 'name'),
                       Parameter.new('std::string&', 'value', direction=Parameter.DIRECTION_OUT)
                   ])

This works, except that the auto-generated C code creates variables that are not used by the wrapper function, causing warnings. In my case, warnings are treated as errors, so it's a problem.