During the past decade, Robin Williams, the thirty-four-year-old comic actor, who seems to connect with his audiences on some wild, deep level and to make them laugh in a special way, at once loud, true, and happy, has been featured in two television programs (“Mork & Mindy” and the 1977 revival of “Laugh-In”), six movies (“Popeye,” “The World According to Garp,” “The Survivors,” “Moscow on the Hudson,” “The Best of Times,” and the forthcoming “Club Paradise”), two concert performances on videocassette, and two record albums (“Reality … What a Concept” and “Throbbing Python of Love”). One kind of performing, however, Williams has been doing non-stop—before, during, and since his television, movie, concert, and recording activities—and that is working out, in unannounced appearances, in small, late-night comedy clubs: in the Comedy…