MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Remove some unneeded headers

Found by 'include-what-you-use'

Cleanup a bit includes

Rework the home directory creation and copy or the skel content to use *at
functions

This allows to simplify the code a bit for -R by not having to keep modifying
path and also prepare the code to improve support -R in userdel

While here, add regression tests for the functionality

readlink len-1

Spelling fixes for usr.sbin/

Stop hard-coding default directory mode as 0777.

Do the right thing with symlinks in the skeleton directory.

PR: bin/63659

Remove unused variables.

Support propogation of file flags when building a homedir from the
skeleton directory.
sprintf() -> snprintf() cleanup.
PR: bin/8756
Submitted by: "Nickolay N. Dudorov" <nnd@itfs.nsk.su>

$Id$ -> $FreeBSD$

Use err(3) instead of local redefinition. Add rcsid string.

Revert $FreeBSD$ to $Id$

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

This commit was generated by cvs2svn to compensate for changes in r20302,
which included commits to RCS files with non-trunk default branches.

Copyright update by the author, to be more in line with our sample
copyright.

Submitted by: David Nugent

Upgrade from the author, reflecting all my wishes resulting out of the
sysinstall use of this tool (plus some bug fixes).

2.2 candidate...

Submitted by: David Nugent <davidn@nserver.usn.blaze.net.au>

pw(8) -- a backend utility to manage the user and group databases.

sysinstall's new User&group menu will use it, hence it's a 2.2
candidate despite of providing new functionality.

Submitted by: David L. Nugent, <davidn@blaze.net.au>