Support annotations on assignment and postfix operations

tests/compiler/dart2js/jumps/data/simple_loops.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 simpleForLoop(count) {
-  for (int i = 0; i < count; i = i + 1) {
+  for (int i = 0; i < count; i++) {
     print(i);
   }
 }
 
 simpleForLoopWithBreak(count) {
   /*0@break*/ for (int i = 0; i < count; i = i + 1) {
     if (i % 2 == 0) /*target=0*/ break;
     print(i);
   }
 }
@@ skipping 213 matching lines @@
   simpleWhileLoopWithLabelledBreak(10);
   simpleWhileLoopWithLabelledContinue(10);
 
   simpleDoLoop(10);
   simpleDoLoopWithBreak(10);
   simpleDoLoopWithContinue(10);
   simpleDoLoopWithBreakAndContinue(10);
   simpleDoLoopWithLabelledBreak(10);
   simpleDoLoopWithLabelledContinue(10);
 }