name: Add std::hash<Name> to support unordered_map container

Change-Id: I1edda483340fc5a891b6ae3a9cc4baf39b859621
Refs: #2147
diff --git a/src/name.hpp b/src/name.hpp
index f4b1411..1719e92 100644
--- a/src/name.hpp
+++ b/src/name.hpp
@@ -597,4 +597,14 @@
 
 } // namespace ndn
 
+namespace std {
+template<>
+struct hash<ndn::Name>
+{
+  size_t
+  operator()(const ndn::Name& name) const;
+};
+
+} // namespace std
+
 #endif