Changed Login to not use its own UIWindow and Removed Unused OK_FBSessionStateChangedNotification

When integrating into a sample iOS Cocos2d-x app, the game's window/view did not receive touch events after the OpenKit login sequence of views and events. One of the commits here fixes this by modifying the OKLogin to not create its own window but merely add the login views to the pre-existing UIWindow.

Is there any particular reason why OKLogin was originally set up to use a separate UIWindow that would make this modification inappropriate?

Also, this fork has removed two lines believed to be unnecessary in the sample app (lines that declare the constant NSString OK_FBSessionStateChangedNotification).

Is it correct that this code no longer serves any purpose?