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

Change-Id: Ie3983d8b6f9929430efd8ada8d942e3f95755cd4
diff --git a/daemon/fw/strategy.cpp b/daemon/fw/strategy.cpp
index ae1b4bd..278e016 100644
--- a/daemon/fw/strategy.cpp
+++ b/daemon/fw/strategy.cpp
@@ -125,7 +125,7 @@
       return {input.getPrefix(i + 1), input[i].toVersion(), input.getSubName(i + 1)};
     }
   }
-  return {input, ndn::nullopt, PartialName()};
+  return {input, nullopt, PartialName()};
 }
 
 Name