Update the constants A_UNSET, A_FUTURE and A_UNKNOWN to their new values.

Their value was changed by Freeciv gna patch #4888 (SVN commit 25394)
Add superficial support for targeted city sabotage and tech theft.

The actual targeting is missing. A random target is chosen just like in their untargeted counter parts. This is done to eliminate a ruleset difference from normal Freeciv.