[CM] SND on OSX

[Bill Schottstaedt]

On the SCM_VARIABLE_REF problem, I think I was being fooled
by several layers of confusion in my home setup (all this time
I thought I was running backwards compatibility tests...) -- xen.h
should have used SCM_CDR for Guile 1.4 and earlier (I think).

On the snd-gfile.c gtk_list_store_remove problem, at some point
gtk changed the return type from void to gboolean (but I can't
find any warning about it anywhere); I just removed all the
previous just-sounds gtk support.

On cacos -- the configure script now tries to compile and
load a program using it; could it be in some library other than
libm.a?  Perhaps libmx?