''MAMMAME,'' which will be seen in its first New York screenings today and tomorrow at Film Forum 2, is the work of Raul Ruiz, the Chilean expatriate film director, and Jean-Claude Gallotta, the French experimentalist choreographer. Mr. Ruiz is a surrealist. Mr. Gallotta is a fabulist. And the surprisingly immediate private worlds of these two enfants terribles of the arts are complementary here. ''MAMMAME,'' which will be seen in its first New York screenings today and tomorrow at Film Forum 2, is the work of Raul Ruiz, the Chilean expatriate film director, and Jean-Claude Gallotta.