I'm not sure I understand the rationale for removing the constraint on
serial numbers - why would you want to encourage (or at least permit)
negative serial numbers? The explanation for a SIZE(1..MAX) constraint
on SET/SEQUENCE is helpful but is not particularly relevant to range
constraints on INTEGER values.
Does anyone see a problem with continuing to restrict CRLNumber (and
CertificateSerialNumber) to being non-negative?
I believe there would be a problem with restricting serial number range
to 0..2^^31-1, since (if I recall correctly) some currently-issued
certificates have 16 octet serial number values (0..2^^127-1).