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/Gizmos/GLGizmosManager.cpp

@@ -6,6 +6,7 @@
 #include "slic3r/GUI/GUI_App.hpp"
 #include "slic3r/GUI/GUI_ObjectManipulation.hpp"
 #include "slic3r/GUI/PresetBundle.hpp"
+#include "slic3r/GUI/Plater.hpp"
 #include "slic3r/Utils/UndoRedo.hpp"
 
 #include "slic3r/GUI/Gizmos/GLGizmoMove.hpp"