Ravel, Maurice: ''Le Tombeau de Couperin.'' Debussy, Claude: ''Danse sacree et danse profane.'' Faure, Gabriel: ''Dolly Suite.'' Ibert, Jacques: Divertissement. Academy of St. Martin in the Fields, Neville Marriner, conductor. (Vanguard Audiophile Digital VA-25019) This delightful record offers an all-French program of divertissement-style music that might be classified elegant easy listening. Marriner conducts all the music with great style, the orchestra plays as well as it always does, and the pressings are first class. It belongs on anyone's shelf of favorite records to relax by.