gpg: Show v3 key fingerprints as all zero.
* g10/keyid.c (fingerprint_from_pk): Show v3 fingerprints as all zero.
MD5 is considered broken for a long time now. To make it easier for
users to notice that a listing shows a v3 key, the fingerprint is now
displayed as 16 zero bytes unless --allow-weak-digest-algos is active.
- Signed-off-by: Werner Koch <wk@gnupg.org>