the previous implementation was not portable at all, assuming
little endian in gf_mulx() and that one can cast unaligned
pointers to ulong in xor128(). also the error code is likely
to be ignored, so better abort() when the length is not a
multiple of the AES block size.
we also pass in full AESstate structures now instead of
the expanded key longs, so that we do not need to hardcode
the number of rounds. this allows each indiviaul keys to
be bigger than 128 bit.
initThumbprints() now takes an application tag argument
so x509 and ssh can coexist.
the thumbprint entries can now hold both sha1 and sha256
hashes. okThumbprint() now takes a len argument for the
hash length used.
the new function okCertificate() hashes the certificate
with both and checks for any matches.
on failure, okCertificate() returns 0 and sets error string.
we also check for include loops now in thumbfiles, limiting
the number of includes to 8.
