convert text into typecode specific data.

def text_to_data(self, text, elt, ps):
        '''convert text into typecode specific data.
        '''
        v = text
        if v == 'false': 
            if self.pyclass is None:
                return False
            return self.pyclass(False)

        if v == 'true': 
            if self.pyclass is None:
                return True
            return self.pyclass(True)

        try:
            v = int(v)
        except:
            try:
                v = long(v)
            except:
                raise EvaluateException('Unparseable boolean', 
                        ps.Backtrace(elt))

        if v:
            if self.pyclass is None:
                return True
            return self.pyclass(True)

        if self.pyclass is None:
             return False
        return self.pyclass(False)