core, core/state, trie: EIP158, reprice & skip empty account write

This commit implements EIP158 part 1, 2, 3 & 4

1. If an account is empty it's no longer written to the trie. An empty
  account is defined as (balance=0, nonce=0, storage=0, code=0).
2. Delete an empty account if it's touched
3. An empty account is redefined as either non-existent or empty.
4. Zero value calls and zero value suicides no longer consume the 25k
  reation costs.

params: moved core/config to params

Signed-off-by: Jeffrey Wilcke <jeffrey@ethereum.org>

cmd/gethrpctest/main.go

@@ -23,7 +23,6 @@ import (
 	"os"
 	"os/signal"
 
-	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -122,7 +121,7 @@ func MakeSystemNode(privkey string, test *tests.BlockTest) (*node.Node, error) {
 	ethConf := &eth.Config{
 		TestGenesisState: db,
 		TestGenesisBlock: test.Genesis,
-		ChainConfig:      &core.ChainConfig{HomesteadBlock: params.MainNetHomesteadBlock},
+		ChainConfig:      &params.ChainConfig{HomesteadBlock: params.MainNetHomesteadBlock},
 	}
 	if err := stack.Register(func(ctx *node.ServiceContext) (node.Service, error) { return eth.New(ctx, ethConf) }); err != nil {
 		return nil, err