Added viewport functionality: The viewport shall estimate if the user is looking at the display (in focus) or not. This is done by vector calculation using roll, pitch and yaw angles. The first usecase is to enable the motion detection feature: It is only active if the user is looking at the display. Still in development state => deactivated by compile switch

Heinrichs Weikamp OSTC4 update files.

The builds are for testing purposes only. Be careful, they might not work and are definitely not recommended for real dives.