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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39745 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/dcclient.cpp

@@ -19,6 +19,7 @@
 #ifndef WX_PRECOMP
     #include "wx/log.h"
     #include "wx/dcmemory.h"
+    #include "wx/math.h" // for floating-point functions
 #endif
 
 #include "wx/image.h"
@@ -28,8 +29,6 @@
 #include "wx/gtk/win_gtk.h"
 #include "wx/gtk/private.h"
 
-#include "wx/math.h" // for floating-point functions
-
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
 #include <gdk/gdkprivate.h>