core: slim down `common.hpp`

Change-Id: I875c35147edd2261fbaa24e809c170d5cd9b94d3
diff --git a/tools/ndn-autoconfig/ndn-fch-discovery.cpp b/tools/ndn-autoconfig/ndn-fch-discovery.cpp
index 0e5c6b0..51234fc 100644
--- a/tools/ndn-autoconfig/ndn-fch-discovery.cpp
+++ b/tools/ndn-autoconfig/ndn-fch-discovery.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2023,  Regents of the University of California,
+ * Copyright (c) 2014-2024,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -181,7 +181,7 @@
     }
     if (statusCode != 200) {
       boost::trim(statusMessage);
-      NDN_THROW(HttpException("HTTP request failed: " + to_string(statusCode) + " " + statusMessage));
+      NDN_THROW(HttpException("HTTP request failed: " + std::to_string(statusCode) + " " + statusMessage));
     }
     std::string header;
     while (std::getline(requestStream, header) && header != "\r")