jsonrpc: Add comment for jsonrpc_msg_to_json().
From a glance at the prototype it wasn't obvious that it destroyed its
argument.
@@ -714,6 +714,9 @@ exit:
return error;
}
+/* Returns 'm' converted to JSON suitable for sending as a JSON-RPC message.
+ *
+ * Consumes and destroys 'm'. */
struct json *
jsonrpc_msg_to_json(struct jsonrpc_msg *m)
{
