Compile issues in latest git with fixes included

[Serpent6877]

OS: Ubuntu 18.04
go version go1.15.6 linux/amd64

# go get -u github.com/OpenBazaar/multiwallet
# github.com/OpenBazaar/multiwallet/keys
/root/go/src/github.com/OpenBazaar/multiwallet/keys/keys.go:48:34: masterPrivKey.Child undefined (type *hdkeychain.ExtendedKey has no field or method Child)
/root/go/src/github.com/OpenBazaar/multiwallet/keys/keys.go:177:3: not enough arguments to return
/root/go/src/github.com/OpenBazaar/multiwallet/keys/keys.go:177:24: km.externalKey.Child undefined (type *hdkeychain.ExtendedKey has no field or method Child)
/root/go/src/github.com/OpenBazaar/multiwallet/keys/keys.go:179:3: not enough arguments to return
/root/go/src/github.com/OpenBazaar/multiwallet/keys/keys.go:179:24: km.internalKey.Child undefined (type *hdkeychain.ExtendedKey has no field or method Child)
# github.com/hunterlong/tokenbalance
/root/go/src/github.com/hunterlong/tokenbalance/tokens.go:94:29: cannot use out (type **big.Int) as type *[]interface {} in argument to _Token.contract.Call
/root/go/src/github.com/hunterlong/tokenbalance/tokens.go:106:29: cannot use out (type **big.Int) as type *[]interface {} in argument to _Token.contract.Call
/root/go/src/github.com/hunterlong/tokenbalance/tokens.go:118:29: cannot use out (type *string) as type *[]interface {} in argument to _Token.contract.Call
/root/go/src/github.com/hunterlong/tokenbalance/tokens.go:130:29: cannot use out (type *string) as type *[]interface {} in argument to _Token.contract.Call

Issue is "github.com/btcsuite/btcutil/hdkeychain/extendedkey.go" code change from Child to Derive.

48c48
< 	fourtyFour, err := masterPrivKey.Derive(hd.HardenedKeyStart + 44)
---
> 	fourtyFour, err := masterPrivKey.Child(hd.HardenedKeyStart + 44)
53c53
< 	bitcoin, err := fourtyFour.Derive(hd.HardenedKeyStart + uint32(coinType))
---
> 	bitcoin, err := fourtyFour.Child(hd.HardenedKeyStart + uint32(coinType))
58c58
< 	account, err := bitcoin.Derive(hd.HardenedKeyStart + 0)
---
> 	account, err := bitcoin.Child(hd.HardenedKeyStart + 0)
63c63
< 	external, err = account.Derive(0)
---
> 	external, err = account.Child(0)
68c68
< 	internal, err = account.Derive(1)
---
> 	internal, err = account.Child(1)
177c177
< 		return km.externalKey.Derive(index)
---
> 		return km.externalKey.Child(index)
179c179
< 		return km.internalKey.Derive(index)
---
> 		return km.internalKey.Child(index)

Additional changes should be done to change all "Child" references to "Derive".