message: Shared child view control for status bar method
diff: - (UIViewController *)navigation_childViewControllerForStatusBarStyle
  {
  - UIViewController *viewController = [[self childViewControllers] lastObject];
  - return [viewController isKindOfClass:[UINavigationController class]] ? ((UINavigationController *) viewController).visibleViewController : nil;
  + return [self childViewControllerForStatusBar];
  }
  - (UIViewController *)navigation_childViewControllerForStatusBarHidden
  +{
  + return [self childViewControllerForStatusBar];
  +}
  +
  +- (UIViewController *)childViewControllerForStatusBar
  {
  UIViewController *viewController = [[self childViewControllers] lastObject];
  return [viewController isKindOfClass:[UINavigationController class]] ? ((UINavigationController *) viewController).visibleViewController : nil;
  