[chuck-users] Exp2

There seems to be no exp2 in 'chuck'. For time efficiency, I thought it might be better to use store intervals in natural base, using log and exp. But it turns out that C99 has both exp2 and log2 and the time difference (in C++) over using exp and log is insignificant; using pow(2, x) takes twice the time. So I think chuck should have both exp2 and log2, and they should call the C99 functions. Hans