Start to work on 5.25 and finish syntax error in eceval

ex-5_23-xx.scm

@@ -39,5 +39,16 @@
 (assert (get-register-contents eceval 'val) 10)
 
 
-(display "\nex-5.25\n")
+(display "\nex-5.25 - lazy-evaluation\n")
+
+(set-register-contents! eceval 'exp
+  '(begin
+     (define (try a b)
+       (if (= a 0) 1 b))
+     (try 0 (/ 1 1))))
+(start eceval)
+(assert (get-register-contents eceval 'val) 1)
+
+
+(display "\nex-5.26\n")