VLCMovieViewController: 360 videos fix rotationlock

on iPad with iOS 9 and higher shouldAutorotate is never called since all orientations are supported by default when
we support multitasking. This lead to no rotationlock when interfacelock was enabled or a 360 video was played.
We're now using supportedInterfaceOrientations: and lock 360 videos to portrait and for interfacelock we save the current orientation and return it.