Newscopy: Not even a curious crowd of New Yorkers can make him smile--Buster Keaton, wife and son arrive for visit, Buster Keaton--he of the icy stare and hero of many movie comedies--arrived in New York yesterday with Natalie Talmadge Keaton and baby Joseph Thomas Keaton, age 4 mos. Buster managed to look dignified for the photographers who kept his family from a belated breakfast when they stepped off the Los Angeles limited.