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    - In Synchronizer, first match a Rollup delayed withdrawn request, with the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      with the delayed withdrawn.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/exittree.go

@@ -3,6 +3,7 @@ package common
 import (
 	"math/big"
 
+	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/iden3/go-merkletree"
 )
 
@@ -30,4 +31,7 @@ type WithdrawInfo struct {
 	Idx             Idx
 	NumExitRoot     BatchNum
 	InstantWithdraw bool
+	TxHash          ethCommon.Hash // hash of the transaction in which the withdraw happened
+	Owner           ethCommon.Address
+	Token           ethCommon.Address
 }