core: slim down `common.hpp`

Change-Id: I875c35147edd2261fbaa24e809c170d5cd9b94d3
diff --git a/tools/ndn-autoconfig/dns-srv.cpp b/tools/ndn-autoconfig/dns-srv.cpp
index bc0b3a6..ee1970e 100644
--- a/tools/ndn-autoconfig/dns-srv.cpp
+++ b/tools/ndn-autoconfig/dns-srv.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2022,  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,
@@ -110,7 +110,7 @@
     NDN_THROW(DnsSrvError("SRV record cannot be parsed (error decoding host name)"));
   }
 
-  return "udp://"s + hostName + ":" + to_string(port);
+  return "udp://"s + hostName + ":" + std::to_string(port);
 }
 
 std::string