[airstrike] Compilation Errors

[Ulf Ekström]

> I changed the CVS makefile so that the produced binary is again
> named 'airstrike' instead of 'testengine' (as the upper level makefile
> expects).

Thanks.
 
> I also added sound support back in:
> - sound effects are now defined in engine/sound_fx.[ch]
> - changed core/sound.* to accept the sound position as vector_t instead
>   of two ints:
>   - changed biplane.c, bird.c & bullet.c accordingly
> - sound support in makefile
> - sound is now on by the default

Oo! Cool! I will test.
 
> Ulf, I think maths.[ch] and array.[ch] could be moved to core/, there's
> nothing Airstrike specific in them.  What do you think?

Ok, seems resonable. On the other hand they also have nothing to do
with the sprite engine that is in core/, maybe we can have a third dir
(misc?).

[..]
 
> The main problem at the moment is that there's only one plane.
> Otherwise I think the game is now better than earlier.

Also you cannot die :-). But soon!

Ulf