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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39694 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/combobox.cpp

@@ -18,10 +18,9 @@
     #include "wx/intl.h"
     #include "wx/settings.h"
     #include "wx/textctrl.h"    // for wxEVT_COMMAND_TEXT_UPDATED
+    #include "wx/arrstr.h"
 #endif
 
-#include "wx/arrstr.h"
-
 // We use GtkCombo which has been deprecated since GTK+ 2.3.0
 // in favour of GtkComboBox for <GTK2.4 runtime
 // We also use GtkList