core: move common.hpp to core/

Headers in core/ are now included as `#include "core/*.hpp"`.
This allows NFD to rely less on include paths when used as a submodule in
another codebase, such as ndnSIM and NFD-Android.

refs #3127

Change-Id: Ia38f3c97427e17ff7b5401281f1fe875b5d5313e
diff --git a/daemon/table/cs-policy-lru.hpp b/daemon/table/cs-policy-lru.hpp
index 81f65bb..2cef234 100644
--- a/daemon/table/cs-policy-lru.hpp
+++ b/daemon/table/cs-policy-lru.hpp
@@ -27,7 +27,7 @@
 #define NFD_DAEMON_TABLE_CS_POLICY_LRU_HPP
 
 #include "cs-policy.hpp"
-#include "common.hpp"
+#include "core/common.hpp"
 
 #include <boost/multi_index_container.hpp>
 #include <boost/multi_index/sequenced_index.hpp>
@@ -103,4 +103,4 @@
 } // namespace cs
 } // namespace nfd
 
-#endif // NFD_DAEMON_TABLE_CS_POLICY_LRU_HPP
\ No newline at end of file
+#endif // NFD_DAEMON_TABLE_CS_POLICY_LRU_HPP