core/vm: move Log to core/types

This significantly reduces the dependency closure of ethclient, which no
longer depends on core/vm as of this change.

All uses of vm.Logs are replaced by []*types.Log. NewLog is gone too,
the constructor simply returned a literal.

eth/api_backend.go

@@ -31,7 +31,7 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
 	"github.com/ethereum/go-ethereum/params"
-	rpc "github.com/ethereum/go-ethereum/rpc"
+	"github.com/ethereum/go-ethereum/rpc"
 	"golang.org/x/net/context"
 )