LIVE_M_MOUTH_BLOCKED            This property indicates that a living is
                                unable to use its mouth. If set, then the
                                living should be unable to speak, whistle,
                                shout, sing. If the property is set to a
                                string, then that string should be printed
                                as fail message when the living tries to use
                                its mouth; if the property is set to any
                                other non-zero value, a default fail message
                                should be printed.
