[5014] Added missing header file.

src/bin/dhcp6/parser_context_decl.h

+// Copyright (C) 2016 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef PARSER6_CONTEXT_DECL_H
+#define PARSER6_CONTEXT_DECL_H
+
+/// @file eval_context_decl.h Forward declaration of the EvalContext class
+
+namespace isc {
+namespace dhcp {
+
+class Parser6Context;
+
+}; // end of isc::eval namespace
+}; // end of isc namespace
+
+#endif