S9fES  (expand-quasiquote list)  ==>  list

If LIST represents a quasiquoted expression, re-write it to an
equivalent expression that uses LIST and APPEND in the place of
quasiquotation. Otherwise return the original list.

(expand-quasiquote '`(a ,b ,@c))  ==>  (append (list 'a) (list b) c)
(expand-quasiquote '(foo bar))    ==>  (foo bar)
