Change extended key version bytes to BIP32

[andyfreer]

-Most compatible solution

[schinzelh]

I'll leave it here for reference: https://www.reddit.com/r/litecoin/comments/48wd2e/why_arent_the_litecoin_bip32_serialization_values/

The proper values are the ones in the reference client. The same convention of using xpub/xprv was also adopted by Electrum-LTC. You may run into software using Ltub/Ltpv, but that format should be considered non-standard.
By the way, let me point out that this is only a presentational matter. Extended keys can be converted from the Ltub/Ltpv convention to the standard one relatively easily.

We'll follow the same path and use xpub/xprv starting with 0.12.1

[schinzelh]

utACK c874a0f

[UdjinM6]

Looks good for me, thanks!