Fix exit table, set delayed_withdrawn in exits

- In exit table, `instant_withdrawn`, `delayed_withdraw_request`, and
  `delayed_withdrawn` were referencing batch_num.  But these actions happen
  outside a batch, so they should reference a block_num.
- Process delayed withdrawns:
    - In Synchronizer, first match a Rollup delayed withdrawn request, with the
      WDelayer deposit (via TxHash), and store the owner and token associated
      with the delayed withdrawn.
    - In HistoryDB: store the owner and token of a delayed withdrawal request
      in the exit_tree, and set delayed_withdrawn when the withdraw is done in
      the WDelayer.
- Update dependency of sqlx to master
    - Last release of sqlx is from 2018 October, and it doesn't support
      `NamedQuery` with a slice of structs, which is used in this commit.

common/block.go

@@ -1,6 +1,7 @@
 package common
 
 import (
+	"math/big"
 	"time"
 
 	ethCommon "github.com/ethereum/go-ethereum/common"
@@ -51,15 +52,30 @@ func NewAuctionData() AuctionData {
 	}
 }
 
+// WDelayerTransfer represents a transfer (either deposit or withdrawal) in the
+// WDelayer smart contract
+type WDelayerTransfer struct {
+	Owner  ethCommon.Address
+	Token  ethCommon.Address
+	Amount *big.Int
+	// TxHash ethCommon.Hash // hash of the transaction in which the wdelayer transfer happened
+}
+
 // WDelayerData contains information returned by the WDelayer smart contract
 type WDelayerData struct {
-	Vars *WDelayerVariables
+	Vars             *WDelayerVariables
+	Deposits         []WDelayerTransfer
+	DepositsByTxHash map[ethCommon.Hash]*WDelayerTransfer
+	Withdrawals      []WDelayerTransfer
 }
 
 // NewWDelayerData creates an empty WDelayerData.
 func NewWDelayerData() WDelayerData {
 	return WDelayerData{
-		Vars: nil,
+		Vars:             nil,
+		Deposits:         make([]WDelayerTransfer, 0),
+		DepositsByTxHash: make(map[ethCommon.Hash]*WDelayerTransfer),
+		Withdrawals:      make([]WDelayerTransfer, 0),
 	}
 }