Add fingerprint record parsing for pgp list keys. (see #3695)
Modify parse_pub_line to parse fpr records and add the fingerprint to
the pgp_key_t's fingerprint field.
Add "--with-fingerprint --with-fingerprint" to the
pgp_list_pubring_command and pgp_list_secring_command commands in
contrib/gpg.rc. The second invocation generates fpr records for subkeys
too.