MFC r328338:

Add SPDX tags for automount(8) et al.

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

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

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Get executable direct maps to work.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make concat() accept NULL arguments.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Options from auto_master must be appended to options from maps,
not prepended.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Properly pass options for direct maps.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make things more readable; no functional changes.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Fix spurious "child process X terminated with exit status 1" messages
from automountd(8).

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Fix automountd(8) not to leave zombies.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make automountd(8) inform autofs(4) whether directory being handled can
have wildcards. This makes it possible for autofs(4) to avoid requesting
automountd(8) action on access to nonexistent nodes - unless wildcards
are actually used.

Note that this change breaks ABI for automountd(8).

Tested by: dhw@
MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Silence down a warning that doesn't provide any useful information unless
debug is enabled.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Add "nobrowse" option. Previously automountd(8) always behaved as if
it was set, now it's conditional.

PR: 192862
MFC after: 2 weeks
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