Generate dynamic type errors according to spec.

tests/language/src/Prefix22Test.dart

Index: tests/language/src/Prefix22Test.dart
===================================================================
--- tests/language/src/Prefix22Test.dart	(revision 5063)
+++ tests/language/src/Prefix22Test.dart	(working copy)
@@ -2,17 +2,17 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
-// Unresolved symbols should be reported as an static type warnings.
+// Unresolved symbols should be reported as static type warnings.
 // This should not prevent execution.
 
 #library("Prefix21NegativeTest.dart");
 #import("library12.dart", prefix:"lib12");
 
 class myClass {
-  myClass(lib12.Library13 p) { // static type warning
+  myClass(lib12.Library13 p) {  /// static type warning
   }
 }
 
 main() {
-  new myClass(null);  // dynamic type error (fix import before making multitest)
+  new myClass(null);  // no dynamic type error when assigning null
 }