The code for CMS data verification was initially written for OpenSSL's
PKCS7_verify() function. It now uses CMS_verify(), but error handling
is still done using PKCS7_verify() error identifiers. Update the
recognized error codes so that the KDC generates
KDC_ERR_DIGEST_IN_SIGNED_DATA_NOT_ACCEPTED errors when appropriate.
Use ERR_peek_last_error() to observe the error generated closest to
the API surface.