If you did not go to high school in St. Louis, and you were to dine at Circa STL (1090 Des Peres Road, Des Peres; 314-394-1196), the new restaurant now open in west county, you might be wise to take a tour guide, or at least a friendly native. The menu turns out to be a crash course into the greatest hits of St. Louis restaurant history — and you can bet a lot of it will go right over your head if you're ordering unassisted.For example: The French onion soup proves to be a riff on the soup made, yes, famous at Famous Barr, the late lamented department store.…