Better error messages for out of range integral values

* This change passes detailed error messages from the JSON parser
  on the server side, back to the client for inclusion into the
  reply's error message.

* Errors originating from the server's inability to parse are
  reclassified from rpcINTERNAL to rpcINVALID_PARAMS.

src/ripple/rpc/impl/ServerHandlerImp.cpp

@@ -569,7 +569,8 @@ ServerHandlerImp::processRequest (Port const& port,
             ! jsonOrig ||
             ! (jsonOrig.isObject () || jsonOrig.isArray()))
         {
-            HTTPReply (400, "Unable to parse request", output, rpcJ);
+            HTTPReply (400, "Unable to parse request: " +
+                       reader.getFormatedErrorMessages(), output, rpcJ);
             return;
         }
     }