[Freeciv-Dev] Submarine nerf

[Per Inge Mathisen <per@xxxxxxxxxxx>]

Based on feedback from a while back on the submarine upgrade, I would like 
to reduce the submarine attack power to 12 (from the current 15). It will 
still be way better than the old sub, which had 10 attack power, 2 less 
movement and 10 more build cost, but it will be easier to defend against 
with escorts.
Let me know if there are any objections to this.

  - Per