Marc,
Ravel did also use the (Eb alto) saxophone as a solo instrument in his orchestration of Musorgsky's "Picture of an Exhibition".
Among the composers which did use the saxophone in classical music are: Bizet,Ravel, Prokofieff, Bartok, Richard Strauss, Rachmaninoff, Debussy, Stravinsky, Kodaly, Puccini (yes, believe it or not), Bernstein, Copland, Berio, Boulez, Zimmerman, Webern, Berg and some others. I do have a complete List somewhere....
Among composers which did use it as a solo instrument are: Jacques Ibert, Claude Debussy, Alexander Glazunov, Frank Martin, Heitor Villa Lobos, Luciano Berio, Philipp Glass and about 10000 others less famous ones.
Iwan
http://www.iwanroth-sax.com