gpg: Cache a once computed fingerprint in PKT_public_key.
* g10/packet.h (PKT_public_key): Add fields fpr and fprlen. * g10/keyid.c (do_fingerprint_md): Remove. (compute_fingerprint): New. (keyid_from_pk): Simplify. (fingerprint_from_pk): Simplify. (hexfingerprint): Avoid using extra array.
This is similar to what we are doing with the keyid for a long time.
- Signed-off-by: Werner Koch <wk@gnupg.org>