Hollywood -- Roddy McDowall’s handsome visage has been insured for $100,000 during the production of the new “Planet of the Apes” television series.   McDowall, who plays a chimpanzee friendly to hunted astronauts in the 20th Century-Fox action-drama for CBS-TV, spends at least 50 hours a week in the tortuous simian makeup.   “It takes three hours to apply the makeup each day,” McDowall said, “It must be stuck to my face to look natural when I speak or make other facial movements.   “It’s an unhealthy situation, basically. When I am in makeup, my skin doesn’t get a chance to breathe. We have worked out a system where every few days I can get a day off to give my skin a chance to breathe again.”   McDowall must subsist on a liquid lunch during production, drinking through a straw. And to smoke a cigarette, he uses a foot-long holder.   Thus far, his skin has been able to sustain the extensive abrasion. His head has not.   “I got a cyst from the wig,” he said. “That’s why I am being insured for the problem of reactions to the makeup.”