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/

Add SPDX tags for automount(8) et al.

MFC after: 2 weeks

Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96

Make things more readable; no functional changes.

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