Includes cleanup:

GUI_App.hpp      (should not include) MainFrame.hpp
MainFrame.hpp    Plater.hpp
ModelArrange.hpp Model.hpp
Slicing.hpp      PrintConfig.hpp
FillBase.hpp     PrintConfig.hpp
GUI_App.hpp      PrintConfig.hpp
OptionsGroup.hpp GUI_App.hpp

src/slic3r/GUI/Tab.cpp

@@ -32,6 +32,8 @@
 #include "GUI_App.hpp"
 #include "GUI_ObjectList.hpp"
 #include "ConfigWizard.hpp"
+#include "Plater.hpp"
+#include "MainFrame.hpp"
 #include "format.hpp"
 
 namespace Slic3r {