Add xmllite and xmpp sources to third_party/

third_party/xmllite/xmlconstants.h

Index: third_party/xmllite/xmlconstants.h
diff --git a/third_party/xmllite/xmlconstants.h b/third_party/xmllite/xmlconstants.h
new file mode 100644
index 0000000000000000000000000000000000000000..2f22c6227239033508904a51da9f1b57e00886df
--- /dev/null
+++ b/third_party/xmllite/xmlconstants.h
@@ -0,0 +1,24 @@
+// Copyright 2004 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WEBRTC_LIBJINGLE_XMLLITE_XMLCONSTANTS_H_
+#define WEBRTC_LIBJINGLE_XMLLITE_XMLCONSTANTS_H_
+
+#include "third_party/xmllite/qname.h"
+
+namespace buzz {
+
+extern const char STR_EMPTY[];
+extern const char NS_XML[];
+extern const char NS_XMLNS[];
+extern const char STR_XMLNS[];
+extern const char STR_XML[];
+extern const char STR_VERSION[];
+extern const char STR_ENCODING[];
+
+extern const StaticQName QN_XMLNS;
+
+}  // namespace buzz
+
+#endif  // WEBRTC_LIBJINGLE_XMLLITE_XMLCONSTANTS_H_