Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.
Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96
Commit r279154 changed the API and ABI significantly, and {NZERO} is still
wrong.
Also, preserve errno on success instead of setting it to 0.
PR: 189821
Reported by: bde
Relnotes: yes