speed up small-factor downsampling; e.g. ~15% improvement for 48k->44100
speed up small-factor downsampling; e.g. ~15% improvement for 48k->44100

uklauer/sox,pcqpcq/sox,pcqpcq/sox,cbagwell/sox,pcqpcq/sox,CaptainHayashi/sox,pcqpcq/sox,CaptainHayashi/sox,cbagwell/sox,cbagwell/sox,uklauer/sox,CaptainHayashi/sox,CaptainHayashi/sox,uklauer/sox,cbagwell/sox,uklauer/sox