[CM] fastest way to pass block of samples in and out of s7

[bil at ccrma.Stanford.EDU]

ffitest.c has brief examples, as does s7test.scm.
I need to add something to s7-ffi.html!  Other
cases are clm-related, in the Snd sources: clm2xen.c,
vct.c, snd-xen.c for example.  In clm2xen.c,
all the clm generators that work with arrays of
doubles give s7 (i.e. the user writing scheme code)
access to that data.  I think this is very similar
to your application.