kerberos5: Migrate from COMPAT_32BIT to generic COMPAT_LIBCOMPAT

[brooks]

I suppose we might consider making this work for COMPAT_LIBCOMPAT=64 in CheriBSD, but it's probably not worth it and our stuff isn't upstream at this point.

[emaste]

I suppose we might consider making this work for COMPAT_LIBCOMPAT=64 in CheriBSD

It seems like that one would be fairly low on the priority list, at least until updated Heimdal / MIT kerberos efforts take place.

[jrtc27]

This is about making kerberos link against openldap from ports, which is pretty niche (I wonder if anyone is even still doing it?). OPENLDAP is in __DEFAULT_NO_OPTIONS.