Add crashing test.

tests/language/div_with_power_of_two2_test.dart

Index: tests/language/div_with_power_of_two2_test.dart
===================================================================
--- tests/language/div_with_power_of_two2_test.dart	(revision 27746)
+++ tests/language/div_with_power_of_two2_test.dart	(working copy)
@@ -98,5 +98,8 @@
         Expect.equals(res, f(arg));
       }
     }
+     Expect.throws(() => divBy0(4),
+                  (e) => e is IntegerDivisionByZeroException
+                         || e is RuntimeError);
   }
 }