Ported test_fill from upstream Slic3r, thanks @lordofhyphens

src/libslic3r/Fill/Fill.hpp

@@ -29,8 +29,6 @@ public:
     FillParams   params;
 };
 
-void make_fill(LayerRegion &layerm, ExtrusionEntityCollection &out);
-
 } // namespace Slic3r
 
 #endif // slic3r_Fill_hpp_

src/libslic3r/Fill/FillBase.hpp

@@ -15,6 +15,7 @@
 
 namespace Slic3r {
 
+class ExPolygon;
 class Surface;
 
 struct FillParams