Next to eating broccoli and brushing teeth, watching historical documentaries has to be kids' least favorite but-it's-good-for-you chore. Headline Stories of the Century solves the problem by reducing the happenings of the entire 20th century into 300-plus eye-grabbing vignettes — some as brief as 30 seconds, none longer than 2 minutes — and packaging them all in four 95- to 108-minute tapes entitled World War II, America in Sports, America in the News (important headline events), and American Nostalgia (pop-culture phenomena). Although the production style is that of old-time movie newsreels, the effect is that of getting 92 years of American history in a palatable, high-energy, visual zap. A