fix(api): remove UNDEFINED

modules/angular2/src/core/compiler/element_injector.ts

@@ -13,7 +13,6 @@ import {
   Injector,
   ProtoInjector,
   Visibility,
-  UNDEFINED,
   Key,
   Dependency,
   bind,
@@ -25,6 +24,7 @@ import {
   resolveForwardRef,
   DependencyProvider
 } from 'angular2/src/core/di';
+import {UNDEFINED} from 'angular2/src/core/di/injector';
 import {
   InjectorInlineStrategy,
   InjectorDynamicStrategy,

modules/angular2/src/core/di.ts

@@ -23,8 +23,7 @@ export {
   ProtoInjector,
   BindingWithVisibility,
   DependencyProvider,
-  Visibility,
-  UNDEFINED
+  Visibility
 } from './di/injector';
 export {
   Binding,