trailer released Wednesday for HBO’s documentary “David Holmes: The Boy Who Lived” introduces Holmes as a teen gymnast who had “no concept of fear,” according to his parents, and landed the “best job in the world” as Radcliffe’s adventurous stand-in.Radcliffe added that Holmes “seemed like a cool older brother” while filming the movies throughout his adolescence. But that all changed when Holmes was involved in a stunt gone wrong that resulted in him instantly breaking his neck and spending six months in the hospital.