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/xmltok_impl.h

@@ -0,0 +1,46 @@
+/*
+Copyright (c) 1998, 1999 Thai Open Source Software Center Ltd
+See the file COPYING for copying permission.
+*/
+
+enum {
+  BT_NONXML,
+  BT_MALFORM,
+  BT_LT,
+  BT_AMP,
+  BT_RSQB,
+  BT_LEAD2,
+  BT_LEAD3,
+  BT_LEAD4,
+  BT_TRAIL,
+  BT_CR,
+  BT_LF,
+  BT_GT,
+  BT_QUOT,
+  BT_APOS,
+  BT_EQUALS,
+  BT_QUEST,
+  BT_EXCL,
+  BT_SOL,
+  BT_SEMI,
+  BT_NUM,
+  BT_LSQB,
+  BT_S,
+  BT_NMSTRT,
+  BT_COLON,
+  BT_HEX,
+  BT_DIGIT,
+  BT_NAME,
+  BT_MINUS,
+  BT_OTHER, /* known not to be a name or name start character */
+  BT_NONASCII, /* might be a name or name start character */
+  BT_PERCNT,
+  BT_LPAR,
+  BT_RPAR,
+  BT_AST,
+  BT_PLUS,
+  BT_COMMA,
+  BT_VERBAR
+};
+
+#include <stddef.h>