Fix compilation with boost 1.66.0
Change-Id: Ibf2883a974c834a5281c39a551e6d467d4454501
diff --git a/src/face.hpp b/src/face.hpp
index 236b296..e5ccbba 100644
--- a/src/face.hpp
+++ b/src/face.hpp
@@ -28,15 +28,10 @@
#include "interest-filter.hpp"
#include "encoding/nfd-constants.hpp"
#include "lp/nack.hpp"
+#include "net/asio-fwd.hpp"
#include "security/key-chain.hpp"
#include "security/signing-info.hpp"
-namespace boost {
-namespace asio {
-class io_service;
-} // namespace asio
-} // namespace boost
-
namespace ndn {
class Transport;