Replace the logic used to determine whether key and signer information
is present to use explicit flags in sigcheck_gpg_status[] array. This
is more future-proof, since it makes it possible to add additional
statuses without having to explicitly update the conditions.
Signed-off-by: Michał Górny <mgorny@gentoo.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>