Include wx/combobox.h according to precompiled headers of wx/wx.h (with other minor cleaning).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39625 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/cocoa/combobox.mm

@@ -78,6 +78,8 @@
 
 #if wxUSE_COMBOBOX
 
+#include "wx/combobox.h"
+
 #ifndef WX_PRECOMP
     #include "wx/window.h"
     #include "wx/log.h"
@@ -85,7 +87,6 @@
 #endif // WX_PRECOMP
 
 #include "wx/cocoa/ObjcPose.h"
-#include "wx/combobox.h"
 
 #import <AppKit/NSComboBox.h>
 #import <Foundation/NSNotification.h>
@@ -160,8 +161,6 @@ void wxCocoaNSComboBox::DisassociateNSComboBox(WX_NSComboBox cocoaNSComboBox)
 
 @end // implementation wxPoserNSComboBox
 
-#include "wx/combobox.h"
-
 #include "wx/cocoa/autorelease.h"
 #include "wx/cocoa/string.h"