Eliminate some divisions from rate.c.
Eliminate some divisions from rate.c.

oneman/opus-oneman,Distrotech/celt,mumble-voip/celt-0.11.0,mumble-voip/celt-0.11.0,dezelin/celt,dezelin/celt,Distrotech/celt,mumble-voip/celt-0.11.0,oneman/opus-oneman,oneman/opus-oneman,Distrotech/celt,dezelin/celt