TV Togetherness: Young Fred Savage of "The Wonder Years" and veteran Hume Cronyn will work together in a CBS holiday movie titled "Christmas on Division Street," about a friendship between an upper-class suburban youth and an elderly homeless man. . . . Art Garfunkel and Marvin Hamlisch, working together for the first time, will record the theme song for "Brooklyn Bridge," the new CBS series bowing Sept. 20.