Add Json::to_string:

This allows the declaration for FastWriter to be hidden and makes
conversion of Json::Value objects to strings a little less clunky.

src/ripple/json/impl/json_value.cpp

@@ -18,6 +18,8 @@
 //==============================================================================
 
 #include <beast/module/core/text/LexicalCast.h>
+#include <ripple/json/to_string.h>
+#include <ripple/json/json_writer.h>
 
 namespace Json {
 

src/ripple/json/impl/json_writer.cpp

@@ -17,6 +17,8 @@
 */
 //==============================================================================
 
+#include <utility>
+
 namespace Json
 {
 

src/ripple/json/impl/to_string.cpp

@@ -0,0 +1,30 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012, 2013 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <ripple/json/json_writer.h>
+
+namespace Json
+{
+
+std::string to_string (Value const& value)
+{
+    return FastWriter ().write (value);
+}
+
+} // namespace Json