make headers include headers they depend on, don't rely on the c(xx)

file to do that. (This is a requirement for header precompiling.)

src/GUI/AirportList.cxx

@@ -1,4 +1,3 @@
-#include <string.h>	// strncpy()
 
 #include <Main/globals.hxx>
 #include <Airports/simple.hxx>

src/GUI/AirportList.hxx

@@ -1,11 +1,17 @@
 // AirportList.hxx - scrolling list of airports.
 
 #ifndef __AIRPORTLIST_HXX
+#define __AIRPORTLIST_HXX
+
+#include <simgear/compiler.h>
+#include STL_STRING
 
 #include <plib/pu.h>
 
 #include "puList.hxx"
 
+SG_USING_STD(string);
+
 class FGAirportList;
 
 class AirportList : public puList
@@ -28,5 +34,3 @@ class AirportList : public puList
 };
 
 #endif // __AIRPORTLIST_HXX
-
-// end of AirportList.hxx

src/GUI/menubar.cxx

@@ -10,7 +10,6 @@
 #include <Autopilot/auto_gui.hxx>
 #include <Input/input.hxx>
 #include <Main/globals.hxx>
-#include <Main/fg_props.hxx>
 
 #include "new_gui.hxx"
 #include "menubar.hxx"

src/GUI/menubar.hxx

@@ -8,6 +8,7 @@
 #endif
 
 #include <simgear/compiler.h>	// for SG_USING_STD
+#include <Main/fg_props.hxx>
 
 #include <plib/pu.h>
 

src/Instrumentation/wxradar.cxx

@@ -25,7 +25,6 @@
 #endif
 
 #include <plib/sg.h>
-#include <plib/ssg.h>
 #include <Main/fg_props.hxx>
 #include <Main/globals.hxx>
 #include <Cockpit/panel.hxx>

src/Instrumentation/wxradar.hxx

@@ -23,6 +23,8 @@
 #ifndef _INST_WXRADAR_HXX
 #define _INST_WXRADAR_HXX
 
+#include <plib/ssg.h>
+
 #include <simgear/props/props.hxx>
 #include <simgear/structure/subsystem_mgr.hxx>
 #include <simgear/environment/visual_enviro.hxx>