Move parser and token related libraries into their own subfolder.

pkg/compiler/lib/src/elements/modelx.dart

Index: pkg/compiler/lib/src/elements/modelx.dart
diff --git a/pkg/compiler/lib/src/elements/modelx.dart b/pkg/compiler/lib/src/elements/modelx.dart
index 417cc96815dc697820d920e33d733ba47fc10612..5c74d62e6ad7baaf175bc740ec4b3a7def35714a 100644
--- a/pkg/compiler/lib/src/elements/modelx.dart
+++ b/pkg/compiler/lib/src/elements/modelx.dart
@@ -35,11 +35,11 @@ import '../resolution/tree_elements.dart' show
     TreeElements;
 import '../resolution/typedefs.dart' show
     TypedefCyclicVisitor;
-import '../scanner/token.dart' show
+import '../script.dart';
+import '../tokens/token.dart' show
     EOF_TOKEN,
     ErrorToken,
     Token;
-import '../script.dart';
 import '../tree/tree.dart';
 import '../util/util.dart';