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/bench_test.go

@@ -163,12 +163,12 @@ func benchInsertChain(b *testing.B, disk bool, gen func(int, *BlockGen)) {
 	// Generate a chain of b.N blocks using the supplied block
 	// generator function.
 	genesis := WriteGenesisBlockForTesting(db, GenesisAccount{benchRootAddr, benchRootFunds})
-	chain, _ := GenerateChain(nil, genesis, db, b.N, gen)
+	chain, _ := GenerateChain(params.TestChainConfig, genesis, db, b.N, gen)
 
 	// Time the insertion of the new chain.
 	// State and blocks are stored in the same DB.
 	evmux := new(event.TypeMux)
-	chainman, _ := NewBlockChain(db, &ChainConfig{HomesteadBlock: new(big.Int)}, FakePow{}, evmux)
+	chainman, _ := NewBlockChain(db, &params.ChainConfig{HomesteadBlock: new(big.Int)}, FakePow{}, evmux)
 	defer chainman.Stop()
 	b.ReportAllocs()
 	b.ResetTimer()