Add utility functions for blocks and transactions witness data

Roasbeef commented 8 years ago

This PR adds a number of utility messages that will be useful for callers interacting with blocks and transactions that contain witness data:

The first new method btcutil.Block.BytesNoWitness provides a helper message to generate a serialized version of a block without any witness data (if any).
The second new method btcutil.Tx.WitnessHash is equivelant to tx.Hash but instead returns the wtxid of a transaction.
The finally added method is btcutil.Tx.HasWitness, which is ideneitcal to tx.HasWitness, but caches the results. This is a useful performance optimization as a transaction may potentially have thousands of inputs, so we avoid interacting over them repeatedly during block validation and other contexts.

NOTE: This PR requires btcsuite/btcd#656

halseth commented 7 years ago

Bech32 PR is up #100

Roasbeef commented 7 years ago

Modified this PR to eliminate the segwit address portion as that portion will now be implemented by #100.

davecgh commented 7 years ago

Would you update the title and descriptions please?

davecgh commented 7 years ago

Need a rebase and then I'll get this merged.

btcsuite / btcutil