Added wxPopupWindow to GTK port, wxComboBox had to

be adapted a little but basically works not under
  GTK/Univ.
  I am pretty sure I forgot some file...


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@10887 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/popupwin.h

@@ -50,6 +50,8 @@ public:
 // include the real class declaration
 #ifdef __WXMSW__
     #include "wx/msw/popupwin.h"
+#elif __WXGTK__
+    #include "wx/gtk/popupwin.h"
 #else
     #error "wxPopupWindow is not supported under this platform."
 #endif