Implement DragAcceptFiles() only when wxUSE_DRAG_AND_DROP==1

This virtual method is implemented in wxWindowBase class only when
wxUSE_DRAG_AND_DROP==1, so it should be re-implemented in the derived class
wxWindowMac also only when wxUSE_DRAG_AND_DROP==1.

src/osx/window_osx.cpp

@@ -639,13 +639,12 @@ void wxWindowMac::SetDropTarget(wxDropTarget *pDropTarget)
     GetPeer()->SetDropTarget(m_dropTarget) ;
 }
 
-#endif
-
 // Old-style File Manager Drag & Drop
 void wxWindowMac::DragAcceptFiles(bool WXUNUSED(accept))
 {
     // TODO:
 }
+#endif
 
 // From a wx position / size calculate the appropriate size of the native control