New XS framework for C and C++ code

xs/xsp/TriangleMesh.xsp

@@ -0,0 +1,14 @@
+%module{Slic3r::TriangleMesh::XS};
+%package{Slic3r::TriangleMesh::XS};
+
+%{
+PROTOTYPES: DISABLE
+
+std::string
+hello_world()
+  CODE:
+    RETVAL = "Hello world!";
+  OUTPUT:
+    RETVAL
+
+%}

xs/xsp/XS.xsp

@@ -0,0 +1,6 @@
+%module{Slic3r::XS};
+%package{Slic3r::XS};
+
+%{
+#include <myinit.h>
+%}

xs/xsp/typemap.xspt

@@ -0,0 +1,2 @@
+%typemap{std::string}{simple};
+%typemap{std::string&}{reference};