register a builtin, create a new wrapper.

def RegisterBuiltin(cls, arg):
        '''register a builtin, create a new wrapper.
        '''
        if arg in cls.types_dict:
            raise RuntimeError, '%s already registered' %arg
        class _Wrapper(arg):
            'Wrapper for builtin %s\n%s' %(arg, cls.__doc__)
        _Wrapper.__name__ = '_%sWrapper' %arg.__name__
        cls.types_dict[arg] = _Wrapper