Tuesday, April 23-Tuesday, July 9, 10-10:30 p.m. EST, on PBS: "Jean Shepherd's America." It's not really possible to describe this humorist and writer; he has a loyal following among college students and listeners of public radio, but he's not trendy. Definitely not trendy. Perhaps it will help to quote the title of next week's segment, a historical tribute to beer: "From Its Ice-Cold Golden Depths Come the Echoes of Lost Battles, the Sound of Ancient Victories, the Noise of a Million Ballgames." If you're smiling, tune in.