add a header placeholder

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43114 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/include/wx/mac/popupwin.h b/include/wx/mac/popupwin.h
new file mode 100755 (executable)
index 0000000..e230fcc
--- /dev/null
+++ b/include/wx/mac/popupwin.h
@@ -0,0 +1,5 @@
+#ifdef __WXMAC_CLASSIC__
+#error "wxPopupWindow is not supported under this platform."
+#else
+#include "wx/mac/carbon/popupwin.h"
+#endif