#27 uncovered hexes become invisible when placing reinforcements

[mranderson2007]

When fog of war is active, placing reinforcements causes hexes that have been uncovered by a passing unit to become invisible again.
e. g.
- start a scenario in which you have airplanes
- request reinforcements
- end turn
- In your next turn, fly with an airplane deep into territory that is covered by the fog of war. The path the unit has taken becomes visible.
- place your reinforcements
- the path that has been uncovered is covered again, although the turn has not ended

This visibility also is not persistent when saving and then reloading a game.