[CM] Snd 25.4

[bil at ccrma.Stanford.EDU]

Snd 25.4

s7: exit has an optional second argument: #t means
   run all c-object gc_free methods before exiting
   (thanks to Victor Lazzarini for pointing out the
   need for this).

   clang++ support is worse

checked: sbcl 2.5.4

Thanks!:  Victor Lazzarini (Csound+s7), Norman Gray