MFC r250378:

Make errbuf optional, so if a caller is not interested in an error
message she can pass NULL (procstat(1) already does this).


git-svn-id: svn://svn.freebsd.org/base/stable/9@252410 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC	r252259:

Minor sort.


git-svn-id: svn://svn.freebsd.org/base/stable/9@252420 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Merge remote-tracking branch 'upstream/svn_stable_9' into svn_stable_9