[PATCH] Ranged attack spread should be varied by distance

[sanderd17]

When ranged units or ballistas are close to their target, their projectile is sometimes ridiculously far off. While it looks plausible on further distances.

So I suggest making the spread variable by distance.

This patch used the spread defined in the attack component to be the spread on the maximum range, and makes the spread smaller for anything else.

[wraitii]

This seems to be a no-brainer good patch to me (as far as design goes).

[wraitii]

In 14425:

Spread is now linearly tied to distance to target. Fixes #2093 .

[wraitii]

Committed in a slightly different version this morning, so it can be tested and reverted if not satisfactory.

I've made the relation linear as this makes more sense and is faster anyway. I've also kept the velocity thingy already in the code now.