[release/1.4.8] core: update DAO soft-fork number, clean up the code

(cherry picked from commit ba784bdf36)

core/vm_env.go

@@ -25,10 +25,6 @@ import (
 	"github.com/ethereum/go-ethereum/core/vm"
 )
 
-// BlockedCodeHashes is a set of EVM code hashes that this node should block
-// sending funds from.
-var BlockedCodeHashes map[common.Hash]struct{}
-
 // GetHashFn returns a function for which the VM env can query block hashes through
 // up to the limit defined by the Yellow Paper and uses the given block chain
 // to query for information.