Initial commit of the new Pressure Equalizer, the EdgeGrid

signed distance field structure.
The EdgeGrid is used to avoid placing the seams on overhangs.

xs/xsp/GCodePressureEqualizer.xsp

@@ -0,0 +1,32 @@
+%module{Slic3r::XS};
+
+%{
+#include <xsinit.h>
+#include "libslic3r/GCode/PressureEqualizer.hpp"
+%}
+
+%name{Slic3r::GCode::PressureEqualizer} class GCodePressureEqualizer {
+    GCodePressureEqualizer(StaticPrintConfig* config)
+        %code%{ RETVAL = new GCodePressureEqualizer(dynamic_cast<GCodeConfig*>(config)); %};
+    ~GCodePressureEqualizer();
+    
+    void reset();
+
+    // Process a next batch of G-code lines. Flush the internal buffers if asked for.
+//    const char* process(const char *szGCode, bool flush);
+//    std::string process(const char *szGCode, bool flush)
+//        %code{% const char *out = THIS->process(szGCode, flush); RETVAL = (out == NULL) ? "" : std::string(out); %};
+
+%{
+
+SV*
+GCodePressureEqualizer::process(const char *szGCode, bool flush)
+    CODE:
+        const char *out = THIS->process(szGCode, flush);
+        RETVAL = newSVpv(out, THIS->get_output_buffer_length());
+    OUTPUT:
+        RETVAL
+
+%}
+
+};