Include wx/scopedptr.h in the code using wxScopedPtr<>

Don't rely on this header from being included from another header (which
won't be the case soon any more).

src/msw/dib.cpp

@@ -39,6 +39,7 @@
 #include "wx/file.h"
 #include "wx/quantize.h"
 #include "wx/scopedarray.h"
+#include "wx/scopedptr.h"
 
 #include <stdio.h>
 #include <stdlib.h>