Return matched tx indices from NewMerkleBlock. (#10)
Return matched tx indices from NewMerkleBlock. (#10)

This commit modifies the NewMerkleBlock function to return the matched
transaction indices instead of their hashes.  This is being done because
it is much easier for the caller to lookup the matched transactions from
the original passed block based on their transaction index within the
block versus their hashes.
decred/dcrd,jrick/dcrd,jrick/btcd,jrick/btcd,jrick/btcd,jrick/dcrd,decred/dcrd