gpg: Print info about the used AEAD algorithm.
* g10/misc.c (openpgp_cipher_algo_mode_name): New. * g10/decrypt-data.c (decrypt_data): Use function here.
With out this change we would see
gpg: cipher algorithm 'AES256' may not be used in --compliance=de-vs mode
This is confusing because AES256 is compliant. Now we see
gpg: cipher algorithm 'AES256.OCB' may not be used in --compliance=de-vs mode
which gives a hint on the problem.