Include expat parser into the Slic3r source code tree.

Having the expat parser inside the Slic3r source base makes life easier
on non-Linux systems and it also allows us to configure the Expat
parser for maximum performance by disabling all unneeded features.

xs/src/expat/expat_config.h

@@ -0,0 +1,33 @@
+/*================================================================
+** Copyright 2000, Clark Cooper
+** All rights reserved.
+**
+** This is free software. You are permitted to copy, distribute, or modify
+** it under the terms of the MIT/X license (contained in the COPYING file
+** with this distribution.)
+*/
+
+#ifndef EXPATCONFIG_H
+#define EXPATCONFIG_H
+
+#include <memory.h>
+#include <string.h>
+
+#define XML_NS 1
+#define XML_DTD 1
+#define XML_CONTEXT_BYTES 1024
+
+/* we will assume all Windows platforms are little endian */
+#define BYTEORDER 1234
+
+/* Windows has memmove() available. */
+#define HAVE_MEMMOVE
+
+#ifdef WIN32
+	#define WIN32_LEAN_AND_MEAN
+	#include <windows.h>
+	#undef WIN32_LEAN_AND_MEAN
+#else
+#endif
+
+#endif /* ifndef EXPATCONFIG_H */