PHOTOGRAPHS - Anti-U.S. Riots flare in Japan. Tokyo policeman, with shield in right hand, grasps hair of a student during riot in the Japanese capital. Students demonstrated against the opening of a new U. S. Army hospital for wounded U. S. soldiers from Vietnam. A pitched battle raged for more than an hour between police and students who tried to storm into the military hospitals compound. Although Japan officially supports the U. S. stand in Vietnam, there have been frequent anti-U.S. demonstrations by students