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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38885 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/mac/carbon/display.cpp

@@ -25,9 +25,12 @@
 
 #if wxUSE_DISPLAY
 
+#include "wx/display.h"
+
 #ifndef WX_PRECOMP
     #include "wx/dynarray.h"
     #include "wx/log.h"
+    #include "wx/string.h"
 #endif
 
 #ifdef __DARWIN__
@@ -41,10 +44,8 @@
     #include <Debugging.h>
 #endif
 
-#include "wx/display.h"
 #include "wx/display_impl.h"
 #include "wx/gdicmn.h"
-#include "wx/string.h"
 
 // ----------------------------------------------------------------------------
 // display classes implementation