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/bitmap.cpp

@@ -17,6 +17,7 @@
     #include "wx/dcmemory.h"
     #include "wx/palette.h"
     #include "wx/icon.h"
+    #include "wx/math.h"
 #endif
 
 #include "wx/filefn.h"
@@ -32,8 +33,6 @@
 
 #include <gdk/gdkimage.h>
 
-#include "wx/math.h"
-
 extern void gdk_wx_draw_bitmap     (GdkDrawable  *drawable,
                           GdkGC               *gc,
                           GdkDrawable  *src,