Add generateAddress utility

nimbus/utils/addresses.nim

@@ -0,0 +1,4 @@
+import nimcrypto, eth_common, rlp
+
+proc generateAddress*(address: EthAddress, nonce: AccountNonce): EthAddress =
+  result[0..19] = keccak256.digest(rlp.encodeList(address, nonce).toOpenArray).data[12..31]

nimbus/vm/interpreter/opcodes_impl.nim

@@ -12,7 +12,7 @@ import
   ./gas_meter, ./gas_costs, ./opcode_values, ./vm_forks,
   ../memory, ../message, ../stack, ../code_stream, ../computation,
   ../../vm_state, ../../errors, ../../constants, ../../vm_types,
-  ../../db/[db_chain, state_db]
+  ../../db/[db_chain, state_db], ../../utils/addresses
 
 # ##################################
 # Syntactic sugar