Support incoming-call status bar height

Status bar is became wider by got incoming call. It makes window frame height smaller. In this situation, window height is 548px and status bar is 40px. Therefore, Navigation bar area has more 20px height. 

Currently `UIViewController+NJKFullScreenSupport` represent like below screenshot.
![ios apr 11 2014 2 44 21 pm](https://cloud.githubusercontent.com/assets/113420/2849922/29e3dc00-d0ec-11e3-9055-a8a21a70d518.png)

This patch add incomming-call status bar support.
![ios apr 11 2014 2 34 02 pm](https://cloud.githubusercontent.com/assets/113420/2849924/2d4a41fe-d0ec-11e3-943c-6f81bf8f44bc.png)