Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r248854:

Reverse the order of some implicit commands (FS mounts and ifconfigs)
when stopping jails. This matters particularly for nested filesystem
mounts.

PR: kern/177325
Submitted by: Harald Schmalzbauer

MFC r239601:

Remember that I'm using length-defined strings in parameters:

Remove a bogus null terminator when stripping the netmask from
IP addresses. This was causing later addresses in a comma-separated
string to disappear.

Use memcpy instead of strcpy. This could just cause Bad Things.

MFC r239602:

Pre-separate IP addresses passed on the command line, so they can be
properly parsed for interface prefixes and netmask suffixes. This was
already done for the old-style (fixed) command line, but missed for
the new-style.

MFC r239621:

Partially roll back r239601 - keep parameter strings both length-delimited
and null-terminated at the same time, because they're later passed to
libjail as null-terminated. That means I also need to add a nul byte when
comma-combining array parameters.

PR: 170832

MFC r234712, r234744, r234934, r234988, r235294, r235335,
and bits of r235337 and r235355:

A new jail(8) with a configuration file, ultimately to replace the work
currently done by /etc/rc.d/jail.

A new jail(8) with a configuration file, ultimately to replace the work
currently done by /etc/rc.d/jail.

MFC after: 3 months

Use the defvs_ruleset paramater when mounting a jail's /dev,
instead of a mount.devfs.ruleset pseudo-parameter.

Following r222465:

Check for IPv4 or IPv6 to be available by the kernel to not
provoke errors trying to query options not available.
Make it possible to compile out INET or INET6 only parts.

Linty stuff.

Update copyright dates and other whitespacey stuff.

Split run_command up into an outer function (next_command) that chooses
a single command string to run, and an inner function (run_command) that
runs that single string.
Move the list of start/stop commands to run from a switch statement into
an array, with a new placeholder parameter IP__OP for actually creating
or removing the jail.
When jail creation fails, revert all non-exec commands in reverse order.

Change cfstrings from an STAILQ into a TAILQ to allow commands to be
traversed in reverse order.

Reads the mount.fstab file, and put its lines separately into the
IP__MOUNT_FROM_FSTAB internal parameter.

Combine check_intparams() and ip_params(), JF_CHECKINT and JF_IPPARAMS.

Use a little more "ifdef INET6".

Keep all internal/known parameter names in one place, and use
enum constants everywhere else.

Initial work on the new jail(8). There are more features to add, and some
cleaning up to do on existing features, but this is pretty much what the
final product will look like.