core: drop std::function and ndn::Exclude from common.hpp, add ndn::optional

Change-Id: Ie3983d8b6f9929430efd8ada8d942e3f95755cd4
diff --git a/tools/nfdc/rib-module.cpp b/tools/nfdc/rib-module.cpp
index a5a2454..47acd0c 100644
--- a/tools/nfdc/rib-module.cpp
+++ b/tools/nfdc/rib-module.cpp
@@ -258,7 +258,7 @@
 
 void
 RibModule::fetchStatus(Controller& controller,
-                       const function<void()>& onSuccess,
+                       const std::function<void()>& onSuccess,
                        const Controller::DatasetFailCallback& onFailure,
                        const CommandOptions& options)
 {