Provide a signing-key-is-revoked flag. Change all callers.
* status.h, status.c (get_status_string): New REVKEYSIG status tag for a
good signature from a revoked key.
* mainproc.c (do_check_sig, check_sig_and_print): Use it here.
* import.c (import_revoke_cert, merge_blocks, merge_sigs): Compare actual
signatures on import rather than using keyid or class matching. This does
not change actual behavior with a key, but does mean that all sigs are
imported whether they will be used or not.
* parse-packet.c (parse_signature): Don't give "signature packet without
xxxx" warnings for experimental pk algorithms. An experimental algorithm
may not have a notion of (for example) a keyid (i.e. PGP's x.509 stuff).