[CM] [SND] Files from (save-region) can't be read by other applications

[bil at ccrma.Stanford.EDU]

I changed this to use default-output-header-type.  Snd
used mus-next because it stores data as doubles, and it's
simpler to write/read double samples, but mus-riff does not
support that sample type (or didn't the last time I looked).
So you'll need to use:

   (save-region r (format #f "test~A.wav" iterator)
     :header-type mus-riff :sample-type mus-lfloat)

I should also check that default choices are compatible...