Problems determining if an attack is a "land bombardment"
This is continuation for #42960 reported by log65536. After the fix in that ticket, we have an issue that Ship attacking Helicopter from a city counts as Land Bombardment. This is impossible to solve without a ruleset format change (thus this is targeted to 3.1+), to somehow give different behavior depending on if target is a Land unit or Helicopter (they both can exist in their current tile, and also in the city where the ship is attacking from).
As part of #43200, this has also been posted to http://forum.freeciv.org/f/viewtopic.php?f=14&t=92057
Attached patches resolve this by adding new unit class flag "NonNatBombardTgt"