json/fwd: add forward declaration header

Makefile.am

@@ -80,6 +80,7 @@ UTIL_FILES   =		\
     ip.cpp		\
     ip.hpp		\
     iterator.hpp	\
+    json/fwd.hpp	\
     json/except.cpp	\
     json/except.hpp	\
     json/flat.cpp	\

json/fwd.hpp

@@ -0,0 +1,35 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_JSON_FWD_HPP
+#define __UTIL_JSON_FWD_HPP
+
+namespace json {
+    namespace tree {
+        class node;
+        class object;
+        class array;
+        class string;
+        class number;
+        class boolean;
+        class null;
+    }
+}
+
+#endif

json/tree.hpp

@@ -30,15 +30,9 @@
 
 #include "../iterator.hpp"
 #include "./flat.hpp"
+#include "./fwd.hpp"
 
 namespace json { namespace tree {
-    class node;
-    class object;
-    class array;
-    class string;
-    class number;
-    class boolean;
-    class null;
 
     /// Parse an encoded form of JSON into a tree structure
     extern std::unique_ptr<node> parse (const boost::filesystem::path &path);