This feature requires a nightly compiler, which should not be required
to build this crate. It will have to be temporarily set for cargo
call-stack.

This reverts commit ff7990f4.

AES-CBC-128 encrypts/decrypts on 16B chunks; if we want to encrypt 8B of
data we must still process a whole 16B chunk. Encrypted output will then
be 16B.

Required for better cargo call-stack.

Messages are now sent every 1/8 seconds.

It would make sense to only write payload bytes if we can consider
publishing those bytes. Writing unencrypted data to the payload first
goes against that sense.