Immortalized in Luchino Visconti’s masterpiece “Death in Venice,” Mahler’s Symphony No. 5 (with its unforgettable Adagietto) today needs no introduction. Except to point out that the composer himself led its premiere some 113 years ago, conducting the Gürzenich Orchestra of Cologne. For this recording, the modern-day players comprising the very same ensemble are led by the city’s newly appointed General Music Director, François-Xavier Roth, which places this version in a class of its own.