2014-12-03: use : list instead of '()

use : list instead of '()

diff --git a/wisp-reader.w b/wisp-reader.w
--- a/wisp-reader.w
+++ b/wisp-reader.w
@@ -51,7 +51,7 @@ define wisp-pending-port : make-object-p
 ;   try-pending
 
 
-define wisp-pending-sexps '()
+define wisp-pending-sexps : list
 
 define : read-one-wisp-sexp port env
   define : wisp-scheme-read-chunk-env