Merge pull request #4108

8c05237 blockchain: cache next block difficulty after adding a block (moneromooo-monero)

src/cryptonote_core/blockchain.cpp

@@ -3696,6 +3696,7 @@ leave:
 
   // appears to be a NOP *and* is called elsewhere.  wat?
   m_tx_pool.on_blockchain_inc(new_height, id);
+  get_difficulty_for_next_block(); // just to cache it
 
   return true;
 }