[freeciv-ai] (PR#6807) [Bug] fstk suggests to attack non-enemy

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

<URL: http://rt.freeciv.org/Ticket/Display.html?id=6807 >

I was investigating the drastic slowdown reported by Paulz (my computer
ground to a halt on his savegame, I even thought there is an infinite
loop going on).

The following is a part of the problem.  
From Paulz profile I can see that each execution of ai_military_attack
calls fstk around 5 times on average.  This is because fstk suggests a
victim which is not our enemy now, we are next to it, but we cannot
attack it, so we call fstk again.

There is a reason why fstk suggests a non-enemy, it's because this
non-enemy is our "war target" or "enemy-to-be".  Because fstk is also
used to evaluate building wants, it views the "enemy-to-be" as an enemy
so we can build units against them before we actually declare war on them.

When it comes to finding stk for a real unit, this behaviour is not so
desirable though.

I suggest we pass fstk a bool which will force it to skip future enemies
from the evaluation.  At least for now.

G.