Added missing file.

com.oracle.truffle.r.native/fficall/src/common/localecharset_fastr.c

+/*
+ * This material is distributed under the GNU General Public License
+ * Version 2. You may review the terms of this license at
+ * http://www.gnu.org/licenses/gpl-2.0.html
+ *
+ * Copyright (c) 1995-2015, The R Core Team
+ * Copyright (c) 2003, The R Foundation
+ * Copyright (c) 2015, 2016, Oracle and/or its affiliates
+ *
+ * All rights reserved.
+ */
+
+#include <Rinternals.h>
+#include <stdlib.h>
+
+const char *locale2charset(const char *locale)
+{
+	return "UTF-8";
+}
+