Fork aimed at resolving the "tilted head after flying a while" bug

[quantumac]

I created a fork to specifically address the irritating bug where after flying for a while the pilot's view is permanently rolled to one side or the other. My fork basically recomputes the roll from the camera commands and applies an offset to counter the roll drift offset introduced by X-Plane. It also attempts to quantize the floating point calculations so as to minimize numerical precision issues when adding/subtracting offsets to head rotations. Lastly, it sets the head roll first before setting the pitch and yaw angles, and that seems to minimize some of the imprecision in roll introduced by X-Plane.

You can check out the changes at "https://github.com/quantumac/headshake". Feel free to use any of these changes or not.