decode_hex_digest was using hash_digest_size. make it use actual HashType size.
decode_hex_digest was using hash_digest_size. make it use actual HashType size.

GroestlCoin/libgroestlcoin,swansontec/libbitcoin,GroestlCoin/libgroestlcoin,Airbitz/libbitcoin,libtetcoin/libtetcoin-consensus,libmetrocoin/libmetrocoin-consensus,libmetrocoin/libmetrocoin-consensus,kaostao/libbitcoin,Airbitz/libbitcoin,BWallet/libbitcoin,GroestlCoin/libgroestlcoin,libmetrocoin/libmetrocoin-consensus,kaostao/libbitcoin,Airbitz/libbitcoin,BWallet/libbitcoin,swansontec/libbitcoin,libmetrocoin/libmetrocoin-consensus,libmetrocoin/libmetrocoin-consensus,libtetcoin/libtetcoin-consensus,libtetcoin/libtetcoin-consensus,BWallet/libbitcoin,kaostao/libbitcoin,libtetcoin/libtetcoin-consensus,swansontec/libbitcoin,kaostao/libbitcoin,GroestlCoin/libgroestlcoin,Airbitz/libbitcoin,BWallet/libbitcoin,swansontec/libbitcoin,libtetcoin/libtetcoin-consensus