[ndnSIM] Adding signals in the base Link Service

Change-Id: I6c20fe17cf41a7437579d8b5a5a9b8d51293a85a
diff --git a/daemon/face/link-service.hpp b/daemon/face/link-service.hpp
index 618e863..9d6d565 100644
--- a/daemon/face/link-service.hpp
+++ b/daemon/face/link-service.hpp
@@ -138,6 +138,18 @@
    */
   signal::Signal<LinkService, lp::Nack> afterReceiveNack;
 
+  /** \brief signals on Interest sent
+   */
+  signal::Signal<LinkService, Interest> afterSendInterest;
+
+  /** \brief signals on Data sent
+   */
+  signal::Signal<LinkService, Data> afterSendData;
+
+  /** \brief signals on Nack sent
+   */
+  signal::Signal<LinkService, lp::Nack> afterSendNack;
+
 public: // lower interface to be invoked by Transport
   /** \brief performs LinkService specific operations to receive a lower-layer packet
    */