Initial rewrite of the file accessors from Perl to C++.

This is especially important for the extremely slow AMF parser.
Also there is a new file handler for the Prusa Control 'PRUS' format.

xs/src/libslic3r/Format/AMF.hpp

@@ -0,0 +1,15 @@
+#ifndef slic3r_Format_AMF_hpp_
+#define slic3r_Format_AMF_hpp_
+
+namespace Slic3r {
+
+class Model;
+
+// Load an AMF file into a provided model.
+extern bool load_amf(const char *path, Model *model);
+
+extern bool store_amf(const char *path, Model *model);
+
+}; // namespace Slic3r
+
+#endif /* slic3r_Format_AMF_hpp_ */