Use <wx/platform.h> instead of <wx/setup.h>

On non-Unix, the platform selection is in platform.h, not on the command
line using the preprocessor macros from wx-config.

<wx/setup.h> relies on the platform being selected correctly, if it is
included directly, it cannot determine the correct configuration with
Visual Studio.

include/gal/opengl/kiglew.h

@@ -29,7 +29,7 @@
 #define KIGLEW_H_
 
 // Pull in the configuration options for wxWidgets
-#include <wx/setup.h>
+#include <wx/platform.h>
 
 // Apple, in their infinite wisdom, has decided to mark OpenGL as deprecated.
 // Luckily we can silence warnings about its deprecation. This is needed on the GLEW

include/gl_utils.h

@@ -28,8 +28,6 @@
 
 #include <limits>
 
-#include <wx/setup.h>
-
 class GL_UTILS
 {
 public: