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

Change-Id: Ie3983d8b6f9929430efd8ada8d942e3f95755cd4
diff --git a/tools/nfdc/strategy-choice-module.cpp b/tools/nfdc/strategy-choice-module.cpp
index 5f81f7a..004f368 100644
--- a/tools/nfdc/strategy-choice-module.cpp
+++ b/tools/nfdc/strategy-choice-module.cpp
@@ -151,7 +151,7 @@
 
 void
 StrategyChoiceModule::fetchStatus(Controller& controller,
-                                  const function<void()>& onSuccess,
+                                  const std::function<void()>& onSuccess,
                                   const Controller::DatasetFailCallback& onFailure,
                                   const CommandOptions& options)
 {