build: Fix build when std::to_string is not available

Change-Id: If34fcebe17bd7e3de23655680957fa6e0df27676
Refs: #4393
diff --git a/daemon/fw/client-control-strategy.cpp b/daemon/fw/client-control-strategy.cpp
index b4bb601..1de5a58 100644
--- a/daemon/fw/client-control-strategy.cpp
+++ b/daemon/fw/client-control-strategy.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2016,  Regents of the University of California,
+/*
+ * Copyright (c) 2014-2017,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -41,7 +41,7 @@
   }
   if (parsed.version && *parsed.version != getStrategyName()[-1].toVersion()) {
     BOOST_THROW_EXCEPTION(std::invalid_argument(
-      "ClientControlStrategy does not support version " + std::to_string(*parsed.version)));
+      "ClientControlStrategy does not support version " + to_string(*parsed.version)));
   }
   this->setInstanceName(makeInstanceName(name, getStrategyName()));