Moved some math macros (sqr, lerp, clamp) to libslic3r.h

Added UNUSED macro to libslic3r.h, used it to reduce some compile warnings.

Split the Int128 class from Clipper library to a separate file,
extended Int128 with intrinsic types wherever possible for performance,
added new geometric predicates.

Added a draft of new FillRectilinear3, which should reduce overfill near the perimeters in the future.

xs/src/libslic3r/Fill/FillRectilinear3.hpp

@@ -0,0 +1,83 @@
+#ifndef slic3r_FillRectilinear2_hpp_
+#define slic3r_FillRectilinear2_hpp_
+
+#include "../libslic3r.h"
+
+#include "FillBase.hpp"
+
+namespace Slic3r {
+
+class Surface;
+
+class FillRectilinear3 : public Fill
+{
+public:
+    virtual Fill* clone() const { return new FillRectilinear3(*this); };
+    virtual ~FillRectilinear3() {}
+    virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+
+    struct FillDirParams
+    {
+        FillDirParams(coordf_t spacing, double angle, coordf_t pattern_shift = 0.f) : 
+            spacing(spacing), angle(angle), pattern_shift(pattern_shift) {}
+        coordf_t    spacing;
+        double      angle;
+        coordf_t    pattern_shift;
+    };
+
+protected:
+	bool fill_surface_by_lines(const Surface *surface, const FillParams &params, std::vector<FillDirParams> &fill_dir_params, Polylines &polylines_out);
+};
+
+class FillGrid3 : public FillRectilinear3
+{
+public:
+    virtual Fill* clone() const { return new FillGrid3(*this); };
+    virtual ~FillGrid3() {}
+    virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+
+protected:
+	// The grid fill will keep the angle constant between the layers, see the implementation of Slic3r::Fill.
+    virtual float _layer_angle(size_t /* idx */) const { return 0.f; }
+};
+
+class FillTriangles3 : public FillRectilinear3
+{
+public:
+    virtual Fill* clone() const { return new FillTriangles3(*this); };
+    virtual ~FillTriangles3() {}
+    virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+
+protected:
+	// The grid fill will keep the angle constant between the layers, see the implementation of Slic3r::Fill.
+    virtual float _layer_angle(size_t /* idx */) const { return 0.f; }
+};
+
+class FillStars3 : public FillRectilinear3
+{
+public:
+    virtual Fill* clone() const { return new FillStars3(*this); };
+    virtual ~FillStars3() {}
+    virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+
+protected:
+    // The grid fill will keep the angle constant between the layers, see the implementation of Slic3r::Fill.
+    virtual float _layer_angle(size_t /* idx */) const { return 0.f; }
+};
+
+class FillCubic3 : public FillRectilinear3
+{
+public:
+    virtual Fill* clone() const { return new FillCubic3(*this); };
+    virtual ~FillCubic3() {}
+    virtual Polylines fill_surface(const Surface *surface, const FillParams &params);
+
+protected:
+	// The grid fill will keep the angle constant between the layers, see the implementation of Slic3r::Fill.
+    virtual float _layer_angle(size_t /* idx */) const { return 0.f; }
+};
+
+
+}; // namespace Slic3r
+
+#endif // slic3r_FillRectilinear2_hpp_