message: refactor(concatAll): fix typings
diff: import { mergeAll } from './mergeAll';
  -import { OperatorFunction, ObservableInput } from '../types';
  +import { OperatorFunction, ObservableInput, ObservedValueOf } from '../types';
  export function concatAll<T>(): OperatorFunction<ObservableInput<T>, T>;
  export function concatAll<R>(): OperatorFunction<any, R>;
  @@ -61,6 +61,6 @@ export function concatAll<R>(): OperatorFunction<any, R>;
  * @return {Observable} An Observable emitting values from all the inner
  * Observables concatenated.
  */
  -export function concatAll<T>(): OperatorFunction<ObservableInput<T>, T> {
  - return mergeAll<T>(1);
  +export function concatAll<O extends ObservableInput<any>>(): OperatorFunction<O, ObservedValueOf<O>> {
  + return mergeAll(1);
  }
  