Fix compilation with Boost 1.65.0

Change-Id: Ib88b7e13bddb1728dd882c086e97edffdd696f0d
Refs: #4258
diff --git a/tools/ndn-autoconfig/dns-srv.cpp b/tools/ndn-autoconfig/dns-srv.cpp
index 5bfa3d5..f432e2c 100644
--- a/tools/ndn-autoconfig/dns-srv.cpp
+++ b/tools/ndn-autoconfig/dns-srv.cpp
@@ -34,6 +34,8 @@
 #include <arpa/nameser_compat.h>
 #endif
 
+#include <iostream>
+
 namespace ndn {
 namespace tools {
 namespace autoconfig {