CLASSICAL James Galway: ''Nocturne.'' Works by Debussy, Chopin, Hamlisch, Mouquet, Massenet, Stravinsky, Faure, L.Boulanger, Field, Liszt, Grieg. James Galway, flute, National Philharmonic Orchestra, David Measham, conductor. (RCA ARL1-4810 ) - There are records made for the ages - an aural document of an exceptional performance - and then there are records made for sheer listening pleasure. This is the latter. It certainly helps that James Galway is one of the finest flutists around, and knows how to suffuse the music he plays with mood and life. The program leans heavily to the easy-listening side of the concert repertoire, but many favorite melodies are included - Massenet's ''Thais'' Meditation, Liszt's Consolation No. 3, Debussy's ''Claire de lune.'' Now and then, choices of tempo and phrasing seem odd, but Galway makes them work, and they are means of adapting to the breath control of the flutist, as the music here is not necessarily written for a wind instrument. It is handsomely packaged, deftly recorded.