zscore

Copperbox revision 2431.

I've added a module for opcodes. Plus I've decided to generate variable names rather than annotate them directly as Strings, the example from yesterday now becomes:

demo01 :: Doc
demo01 = format $ runInstBuilder 199 $ do
   iamp <- ivar $ pfield 4
   ifrq <- ivar $ cpspch (pfield 5)   
   a1   <- oscil iamp ifrq 1
   out a1