Return an explicit empty list in s-exp
Return an explicit empty list in s-exp

Before we used dyanmicNil, which, while equivalent to the empty list,
isn't quite the same thing. This new approach ensures an empty list is
actually printed to the REPL.

eriksvedang/Carp,carp-lang/Carp,carp-lang/Carp,eriksvedang/Carp,carp-lang/Carp