-Fix (#161): a deviated unit was never attacked by turrets of his former ally
-Fix (#161): deviated units weren't seen as enemies by script

This also fixes that a deviated unit kept shooting its current target
-Codechange: name all FindTarget functions the same, also their local variables
-Codechange: don't do checks you check a few lines lower too, but in a child function
-Codechange: Unit_SetTarget(unit, 0) does not set the target to none (but does nothing instead)

Also, make deviate function consistent (reset target and destination in
both when you get deviated, as when you lose deviation)
-Codechange: use Unit_GetHouseID, just to be sure