[airstrike] Missile "Bonus"

[Ulf Ekström]

> and the missiles should be stabilized by the airstream, i.e. turn the
> nose towards their heading. The lack of this is especially striking when
> a missile runs out of fuel. Using the formula for biplanes stabilizes
> the missile 90 degrees off of its course. To understand the formula and
> apply it to missiles I need some time and ease.

Maybe it's just that the animation is out of synch. If I remember
correctly the "tip" of an object shought be pointing to the right in
frame 0, it could be that the missile is 90 degrees off. I can have a
look.

Ulf