update source program to match x86 code for sum of first five

Author: jsiek

book.tex

@@ -10923,12 +10923,13 @@ \chapter{Loops and Dataflow Analysis}
 \begin{lstlisting}
 (let ([sum 0])
   (let ([i 5])
-    (begin
-      (while (> i 0)
-        (begin
-          (set! sum (+ sum i))
-          (set! i (- i 1))))
-      sum)))
+    (+ 27
+      (begin
+        (while (> i 0)
+          (begin
+            (set! sum (+ sum i))
+            (set! i (- i 1))))
+        sum))))
 \end{lstlisting}
 The \code{while} loop consists of a condition and a
 body.\footnote{The \code{while} loop is not a built-in