The previous version of the function made adding AEAD changes very difficult. This change should be a semantic no-op - it should be purely a cleanup.
Implement ChannelID as both a client and server.
Initial fork from f2d678e6e89b6508147086610e985d4e8416e867 (1.0.2 beta). (This change contains substantial changes from the original and effectively starts a new history.)
