Carlos Reygadas, the Mexican director of the justly praised Japon, had Battle In Heaven, his second, booed at his Cannes press showing. It is one of the strangest movies in this year's competition, starting and ending with sex scenes that rival anything in Michael Winterbottom's Nine Songs. The central character is a fat, middleaged Mexican who is the chauffeur for an army general but who, to augment his income, indulges in various criminal activities. He and his wife