[Freeciv-Dev] (PR#4199) Planes downed in a grouned attack

["Gregory Berkolaiko" <Gregory.Berkolaiko@xxxxxxxxxxxx>]

I am gearing up to the big movement handling cleanup in server and as a 
part of my research I discovered this:

it there are two units, a plane and a ground unit on the same tile you 
_can_ attack them, provided the ground unit is deemed the better defender.  
In the case of your victory against the ground unit, the plane also falls 
out of the sky.

If the plane is deemed the better unit, the attack is disallowed with 
        Game: You can't attack there
message.

I think a thorough layers patch is the answer.  The latest one, PR#2581, 
is not thorough, unfortunately.

G.