usr.sbin: 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/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

There is no way of escaping literal $ signs in auto_master(5), which
makes for difficulty with hidden Samba shares; shares with $ at the end
of their name. This enables the use of ${DOLLAR} to work around this.

Reviewed by: bcr (man page)
Approved by: trasz
Differential Revision: https://reviews.freebsd.org/D7048

Add SPDX tags for automount(8) et al.

MFC after: 2 weeks

Use proper argument order for calloc(3).

MFC after: 1 month

The <libutil.h> is an ordinary header file; should sort just like any other.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Use __FBSDID() properly.

Suggested by: pluknet@
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation

Bring in the new automounter, similar to what's provided in most other
UNIX systems, eg. MacOS X and Solaris. It uses Sun-compatible map format,
has proper kernel support, and LDAP integration.

There are still a few outstanding problems; they will be fixed shortly.

Reviewed by: allanjude@, emaste@, kib@, wblock@ (earlier versions)
Phabric: D523
MFC after: 2 weeks
Relnotes: yes
Sponsored by: The FreeBSD Foundation