build: update to latest version of btcutil with Litecoin bug fix

Fixes #1949.
Fixes #1985.

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/aead/chacha20 v0.0.0-20180709150244-8b13a72661da // indirect
 	github.com/btcsuite/btcd v0.0.0-20190213025234-306aecffea32
 	github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f
-	github.com/btcsuite/btcutil v0.0.0-20190207003914-4c204d697803
+	github.com/btcsuite/btcutil v0.0.0-20190316010144-3ac1210f4b38
 	github.com/btcsuite/btcwallet v0.0.0-20190313041134-68fc7c82e131
 	github.com/btcsuite/fastsha256 v0.0.0-20160815193821-637e65642941
 	github.com/coreos/bbolt v1.3.2