Removed a broken Arc Fitting feature.

Removed the questionable Pressure Advance feature. It is better to use the Pressure Advance implemented into a firmware.
Added a C++ implementation of GCodeReader and SpiralVase, thanks to @alexrj
Added a C++ implementation of GCodeTimeEstimator, thanks to @lordofhyphens

xs/src/libslic3r/GCode/SpiralVase.hpp

@@ -0,0 +1,29 @@
+#ifndef slic3r_SpiralVase_hpp_
+#define slic3r_SpiralVase_hpp_
+
+#include "libslic3r.h"
+#include "GCode.hpp"
+#include "GCodeReader.hpp"
+
+namespace Slic3r {
+
+class SpiralVase {
+    public:
+    bool enable;
+    
+    SpiralVase(const PrintConfig &config)
+        : enable(false), _config(&config)
+    {
+        this->_reader.Z = this->_config->z_offset;
+        this->_reader.apply_config(*this->_config);
+    };
+    std::string process_layer(const std::string &gcode);
+    
+    private:
+    const PrintConfig* _config;
+    GCodeReader _reader;
+};
+
+}
+
+#endif