Freeciv

I've been unable to find any mention of this in recent changelogs, so I'm assuming it's an unintended bug. If not, it's a monumental mechanical change that's inconsistent with the mechanics of any other Civ game.

This seems to have been introduced in v3.2.0 but wasn't caught when addressing RM#1369.

To replicate: start a new game, grow a city to 3 population, and set that city to happy. While the city interface will indicate celebration on the next turn, actual changes to tile outputs will not take effect until the following turn after that.