(svn r20632) -Cleanup: remove "a few" unneeded includes, and add them to some headers

src/airport.cpp

@@ -10,13 +10,6 @@
 /** @file airport.cpp Functions related to airports. */
 
 #include "stdafx.h"
-#include "debug.h"
-#include "airport.h"
-#include "map_type.h"
-#include "core/alloc_func.hpp"
-#include "date_func.h"
-#include "settings_type.h"
-#include "newgrf_airport.h"
 #include "station_base.h"
 #include "table/strings.h"
 #include "table/airport_movement.h"