Make the public key prefix part of the input to the hash function in RedDSA, not part of the message.
Make the public key prefix part of the input to the hash function in RedDSA, not part of the message.

Signed-off-by: Daira Hopwood <cd7d43d5556a38ce626d53826fddc46adc597539@jacaranda.org>

zcash/zips,zcash/zips,zcash/zips,zcash/zips