Fix compilation with Boost 1.65.0

Change-Id: Ib88b7e13bddb1728dd882c086e97edffdd696f0d
Refs: #4258
diff --git a/tools/ndn-autoconfig/guess-from-identity-name.cpp b/tools/ndn-autoconfig/guess-from-identity-name.cpp
index 8ef112d..9c50c20 100644
--- a/tools/ndn-autoconfig/guess-from-identity-name.cpp
+++ b/tools/ndn-autoconfig/guess-from-identity-name.cpp
@@ -25,9 +25,12 @@
 
 #include "guess-from-identity-name.hpp"
 #include "dns-srv.hpp"
+
 #include <ndn-cxx/security/pib/identity.hpp>
 #include <ndn-cxx/security/pib/pib.hpp>
 
+#include <sstream>
+
 namespace ndn {
 namespace tools {
 namespace autoconfig {