[CM] [Snd] Searching conditionally for starts and ends of phrases

[Bill Schottstaedt]

Since phrase-lookup returns a function, you can use it
either via (scan-channel (phrase-lookup)) or in the C-s
case by typing (phrase-lookup) at the "find:" prompt (the
first time -- it will be re-evaluated on subsequent C-s's).

moving-average divides by its length, so sum-of-squares in
your code is actually sum-of-squares/bufferlen.  See dsp.scm
for one way to implement moving-sum.