Added missing includes (GCC 9.3)

src/libslic3r/ElephantFootCompensation.hpp

@@ -2,6 +2,7 @@
 #define slic3r_ElephantFootCompensation_hpp_
 
 #include "libslic3r.h"
+#include "ExPolygon.hpp"
 #include <vector>
 
 namespace Slic3r {

src/libslic3r/PrintObjectSlice.cpp

@@ -3,6 +3,7 @@
 #include "Layer.hpp"
 #include "MultiMaterialSegmentation.hpp"
 #include "Print.hpp"
+#include "ClipperUtils.hpp"
 
 #include <boost/log/trivial.hpp>