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>

core/chain_makers_test.go

@@ -41,13 +41,16 @@ func ExampleGenerateChain() {
 		db, _   = ethdb.NewMemDatabase()
 	)
 
+	chainConfig := &params.ChainConfig{
+		HomesteadBlock: new(big.Int),
+	}
 	// Ensure that key1 has some funds in the genesis block.
 	genesis := WriteGenesisBlockForTesting(db, GenesisAccount{addr1, big.NewInt(1000000)})
 
 	// This call generates a chain of 5 blocks. The function runs for
 	// each block and adds different features to gen based on the
 	// block index.
-	chain, _ := GenerateChain(nil, genesis, db, 5, func(i int, gen *BlockGen) {
+	chain, _ := GenerateChain(chainConfig, genesis, db, 5, func(i int, gen *BlockGen) {
 		switch i {
 		case 0:
 			// In block 1, addr1 sends addr2 some ether.
@@ -77,7 +80,7 @@ func ExampleGenerateChain() {
 
 	// Import the chain. This runs all block validation rules.
 	evmux := &event.TypeMux{}
-	blockchain, _ := NewBlockChain(db, MakeChainConfig(), FakePow{}, evmux)
+	blockchain, _ := NewBlockChain(db, chainConfig, FakePow{}, evmux)
 	if i, err := blockchain.InsertChain(chain); err != nil {
 		fmt.Printf("insert error (block %d): %v\n", chain[i].NumberU64(), err)
 		return