change default line length to 40 columns

gmi.rkt

@@ -110,7 +110,7 @@
   (define (inner-iter acc rst)
     (let ([line (string-join acc)])
       (if (or (empty? rst)
-              (> (string-length line) 80))
+              (> (string-length line) 40))
           (values acc rst)
           (inner-iter (append acc (list (car rst)))
                       (cdr rst)))))