refactor(patches): move stub to patch file for delayWhen

Author: masaeedu

src/Rx.ts

@@ -48,6 +48,7 @@ export * from './add/operator/debounce';
 export * from './add/operator/debounceTime';
 export * from './add/operator/defaultIfEmpty';
 export * from './add/operator/delay';
+export * from './add/operator/delayWhen';
 export * from './add/operator/distinctUntilChanged';
 export * from './add/operator/do';
 export * from './add/operator/expand';

src/add/operator/delayWhen.ts

@@ -1,6 +1,11 @@
+
 import {Observable} from '../../Observable';
 import {delayWhen} from '../../operator/delayWhen';
 
 Observable.prototype.delayWhen = delayWhen;
 
-export var _void: void;
+declare module '../../Observable' {
+  interface Observable<T> {
+    delayWhen: (delayDurationSelector: (value: T) => Observable<any>, subscriptionDelay?: Observable<any>) => Observable<T>;
+  }
+}