Legiters can now catch little-seen Stephen Sondheim tuner “Anyone Can Whistle” on both sides of the Atlantic, with U.K.-based Primavera Prods. mounting a revival of the show at London’s Jermyn Street Theater in the spring.The 1964 musical satire with book by Arthur Laurents is already on tap for a Gotham staging in April as part of the annual Encores! series of tuner revivals. Both the Primavera and the Encores! productions fall at around the same time as Sondheim’s 80th birthday. Last year Primavera produced a revival of another early Sondheim outing, “Saturday Night,” that attracted attention from London theatergoers. The org’s production of “Anyone Can Whistle,” helmed by “Saturday Night” director Tom Littler, will play March 10-April 17.