Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r235297, r235316:

Add a -v and -N option to kenv(1), so it can be more easily used in
scripts the way sysctl(8) is. The -N option, like in sysctl(8),
displays only the kenv names, not their values. The -v option prints an
individual kenv variable name with its value as name="value". This is
the inverse of sysctl(8)'s -n flag, since the default behaviour of
kenv(1) is already like sysctl(8) -n.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

mdoc(7) markup.

Approved by: avg (mentor), kib (mentor)
MFC after: 3 days

o Fix a typo. Bump .Dd for the previous delta.

fix typo

Submitted by: Colin Percival

Document how kernel environment can be statically compiled in,
and reference a few related manpages.

MFC after: 3 days

-mdoc sweep.

Add a "-q" quiet flag to kenv so that warnings can be suppressed.

MFC after: 1 week

/*- or .\"- or #- to begin license clauses.

kenv(1) has been repo copied from usr.bin to bin.
Sometimes we need kenv(1) in /etc/rc.diskless*.

mdoc(7) police: punctuation.

Add a reference to the kenv(2) manpage.

Use the new functionalities provided by the kenv(2) syscall.

Reviewed by: peter

mdoc(7) police: markup nits.

Spell "FreeBSD" with "F" and "BSD" in uppercase.

mdoc(7) police: removed HISTORY info from the .Os call.

kenv(1) first appeared in FreeBSD 4.1.1, not FreeBSD 5.0.

PR: 23020
Submitted by: Simon Dick <simond@irrelevant.org>

mdoc(7) police: use the new features of the Nm macro.

Initial kenv(1) hack for dumping the kernel environment. This can be
used to extract modified boot hints to make loader(8)-time changes
"sticky". It tries to use \ style quoting so that it can be used directly
with foo.conf files. It can also extract specific variables.