Fix capturing logic

-Fix: capturing with deviated units did not unlock tech

Structure_GetStructuresBuilt is called with the unit's houseID rather  than the structure's new owner's houseID/the unit's current owner.  This means a deviated unit capturing a new structure does not properly unlock tech.  Bug in the original game.

-Fix: windtrap power information incorrect after capturing a windtrap

The game keeps a windtrap count which is used to average the power output.  This value is not adjusted when a windtrap is captured, so the average goes wrong.  I decided to recount the windtraps in Structure_GetStructuresBuilt as that will also fix the count in existing saved games.  Bug in original game, reported by MrFlibble.