usr.bin: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

Drop "All rights reserved" from all my stuff. This includes
Foundation copyrights, approved by emaste@. It does not include
files which carry other people's copyrights; if you're one
of those people, feel free to make similar change.

Reviewed by: emaste, imp, gbe (manpages)
Differential Revision: https://reviews.freebsd.org/D26980

rctl: fix sysctl kern.racct.enable use after r341182

The value was changed from int to bool. Since the new type
is smaller, the rest of the variable in the caller was left
unitialized.

PR: 236714
Reported by: trasz
Diagnosed by: markj
Sponsored by: The FreeBSD Foundation

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.

Remove __unused attributed on arguments that are actually used

MFC after: 3 days

Fix typos in error messages dealing with unknown groups/users

MFC after: 1 month
X-MFC with: r291447, r291452
Sponsored by: EMC / Isilon Storage Division

Fix rctl rule filters - eg the 'rctl -r :' case.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Improve error reporting to clearly show problematic rules.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Simplify rule retrieval and improve error handling.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Fix some memory management problems.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Handle asprintf(3) errors in a standards-compliant way.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Rewrite the rctl(8) utility to make it possible to add multiple rules
in a single run. This speeds up operation with large rulesets.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

User and group identifiers the rctl(8) utility receives from the kernel
are always in numeric form; don't try to resolve them by names. This
speeds up rule listing with large rulesets by about 50%.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make rctl(8) use more reasonable buffer size for retrieving the rules.

Reviewed by: mjg@
MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Remove spurious period.

MFC after: 1 month
Sponsored by: International OCD Foun^W^W^WThe FreeBSD Foundation

Make rctl(8) more user-friendly when RACCT/RCTL is disabled for some reason.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Add rctl(8), the utility to manage rctl rules.

Sponsored by: The FreeBSD Foundation
Reviewed by: kib (earlier version)