sm: Also show the SHA-256 fingerprint.

* sm/keylist.c (list_cert_colon): Emit a new "fp2" record.
(list_cert_raw): Print the SHA2 fingerprint.
(list_cert_std): Ditto.

Backported-from-master: e7d70923901eeb6a2c26445aee9db7e78f6f7f3a

Here in 2.2 we keep the string "fingerprint:" and no not change it to
"sha1 fpr" as we did in master (2.3).

• Signed-off-by: Werner Koch <wk@gnupg.org>