[Freeciv-Dev] Reducing city population after unit's successful attack

[Tomasz Wegrzanowski <maniek@xxxxxxxx>]

Herewith is prototypic patch against Feb23cvs that
provide additional server variable : killcitizen
This is or-flag, which indicates, after successful attack
of which types of units city population should be reduced
(land,sea,heli,air).

Possible uses :
1) balancing ships
2) huge pre-modern wars