contrib-json_spirit:  adding library to reduce external dependencies

moreover, the current macports version is not usable due to a missing
header

Change-Id: I7cd80ecf17b1ca50e5c71badba56d0bf3d390f4f
diff --git a/contrib/json_spirit/json_spirit.h b/contrib/json_spirit/json_spirit.h
new file mode 100644
index 0000000..d574af5
--- /dev/null
+++ b/contrib/json_spirit/json_spirit.h
@@ -0,0 +1,18 @@
+#ifndef JSON_SPIRIT

+#define JSON_SPIRIT

+

+//          Copyright John W. Wilkinson 2007 - 2011

+// Distributed under the MIT License, see accompanying file LICENSE.txt

+

+// json spirit version 4.05

+

+#if defined(_MSC_VER) && (_MSC_VER >= 1020)

+# pragma once

+#endif

+

+#include "json_spirit_value.h"

+#include "json_spirit_reader.h"

+#include "json_spirit_writer.h"

+#include "json_spirit_utils.h"

+

+#endif