Include hardfork.hpp in db_notify.cpp

Author: nathanielhourt

libraries/chain/db_notify.cpp

@@ -17,6 +17,7 @@
 #include <graphene/chain/vesting_balance_object.hpp>
 #include <graphene/chain/transaction_history_object.hpp>
 #include <graphene/chain/impacted.hpp>
+#include <graphene/chain/hardfork.hpp>
 
 using namespace fc;
 using namespace graphene::chain;