(Android) Implement immersive mode on Kitkat

Kitkat has a new fullscreen mode "immersive". It can make the app truly full screen

http://developer.android.com/training/system-ui/immersive.html

The code I take from XBMC https://github.com/xbmc/xbmc/pull/3712

Only enable in game-playing screen. The patch maybe dirty and need to review, at least, it work fine on my Nexus 4(Google official ROM without root).  

Here is a screenshot 

![screenshot_2014-03-17-22-06-12](https://f.cloud.github.com/assets/330812/2436752/6c6e71e6-addf-11e3-97c5-34decb73821e.jpg)