'The primary CILE driver for this multi-lang lang.
This is the CILE driver for the SSL lang, if there is one, otherwise
for the csl_lang.
Side effect: `self.slave_csl_cile_driver\' is determined the
first time this is called. A little gross, I know, but it
avoids having a separate property.'

@property
def master_cile_driver(self):

    if (self._master_cile_driver is None):
        if (self.ssl_lang is not None):
            self._master_cile_driver = self.mgr.citadel.cile_driver_from_lang(self.ssl_lang)
            self.slave_csl_cile_driver = self.mgr.citadel.cile_driver_from_lang(self.csl_lang)
        else:
            self._master_cile_driver = self.mgr.citadel.cile_driver_from_lang(self.csl_lang)
            self.slave_csl_cile_driver = None
    return self._master_cile_driver
