The curtain came down on “Lettice and Lovage’’ at Gloucester Stage Company over the weekend, and afterward American Repertory Theater actor Alvin Epstein sat for a bit with its star, actress Lindsay Crouse. It was a reunion of sorts. In 1989, Epstein played the role of Crouse’s elderly husband in David Mamet’s adaptation of “Uncle Vanya’’ at the ART. Epstein, who celebrated his 90th birthday last year, has worked with many great actors over his career, and writes about some of them in his book, “Dressing Room Stories,’’ including Bert Lahr, Marcel Marceau, Etienne Decroux, Meryl Streep, and a teenage Barbra Streisand.