Move Print object storage to C++. (along with its subobjects)

xs/src/PlaceholderParser.cpp

@@ -0,0 +1,25 @@
+#include "PlaceholderParser.hpp"
+#ifdef SLIC3RXS
+#include "perlglue.hpp"
+#endif
+
+
+namespace Slic3r {
+
+
+PlaceholderParser::PlaceholderParser()
+{
+    // TODO: port these methods to C++, then call them here
+    // this->apply_env_variables();
+    // this->update_timestamp();
+}
+
+PlaceholderParser::~PlaceholderParser()
+{
+}
+
+#ifdef SLIC3RXS
+REGISTER_CLASS(PlaceholderParser, "GCode::PlaceholderParser");
+#endif
+
+}