tx_pool: add a debug message when adding a tx to the pool

src/cryptonote_core/tx_pool.cpp

@@ -255,6 +255,7 @@ namespace cryptonote
 
     m_txs_by_fee_and_receive_time.emplace(std::pair<double, std::time_t>(fee / (double)blob_size, receive_time), id);
 
+    MINFO("Transaction " << id << " added to pool");
     return true;
   }
   //---------------------------------------------------------------------------------