Make HardFork object available to BlockchainDB and derived DB implementations

This will later allow the HardFork object's DB update functions to be
called when the DB transaction that persists across block add/remove is
open.

src/blockchain_db/berkeleydb/db_bdb.cpp

@@ -781,6 +781,8 @@ BlockchainBDB::BlockchainBDB(bool batch_transactions) :
     m_batch_transactions = batch_transactions;
     m_write_txn = nullptr;
     m_height = 0;
+
+    m_hardfork = nullptr;
 }
 
 void BlockchainBDB::open(const std::string& filename, const int db_flags)

src/blockchain_db/blockchain_db.cpp

@@ -138,6 +138,11 @@ uint64_t BlockchainDB::add_block( const block& blk
   return prev_height;
 }
 
+void BlockchainDB::set_hard_fork(HardFork*& hf)
+{
+  m_hardfork = hf;
+}
+
 void BlockchainDB::pop_block(block& blk, std::vector<transaction>& txs)
 {
   blk = get_top_block();

src/blockchain_db/blockchain_db.h

@@ -28,12 +28,15 @@
 #ifndef BLOCKCHAIN_DB_H
 #define BLOCKCHAIN_DB_H
 
+#pragma once
+
 #include <list>
 #include <string>
 #include <exception>
 #include "crypto/hash.h"
 #include "cryptonote_core/cryptonote_basic.h"
 #include "cryptonote_core/difficulty.h"
+#include "cryptonote_core/hardfork.h"
 
 /* DB Driver Interface
  *
@@ -322,6 +325,8 @@ protected:
   uint64_t time_commit1 = 0;
   bool m_auto_remove_logs = true;
 
+  HardFork* m_hardfork;
+
 public:
 
   // virtual dtor
@@ -372,6 +377,8 @@ public:
   virtual void block_txn_stop() = 0;
   virtual void block_txn_abort() = 0;
 
+  virtual void set_hard_fork(HardFork*& hf);
+
   // adds a block with the given metadata to the top of the blockchain, returns the new height
   // NOTE: subclass implementations of this (or the functions it calls) need
   // to handle undoing any partially-added blocks in the event of a failure.

src/blockchain_db/lmdb/db_lmdb.cpp

@@ -945,6 +945,8 @@ BlockchainLMDB::BlockchainLMDB(bool batch_transactions)
   m_write_batch_txn = nullptr;
   m_batch_active = false;
   m_height = 0;
+
+  m_hardfork = nullptr;
 }
 
 void BlockchainLMDB::open(const std::string& filename, const int mdb_flags)

src/cryptonote_core/blockchain.cpp

@@ -290,6 +290,8 @@ bool Blockchain::init(BlockchainDB* db, const bool testnet, const bool fakechain
   }
   m_hardfork->init();
 
+  m_db->set_hard_fork(m_hardfork);
+
   // if the blockchain is new, add the genesis block
   // this feels kinda kludgy to do it this way, but can be looked at later.
   // TODO: add function to create and store genesis block,