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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

sys: 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.

Rework netisr policy mechanism so that per-protocol dispatch policies can
be represented:

- A single policy namespace is defined, consisting of four possible
policies: "default" to use the global default, "deferred" to force
deferred dispatch, "direct" to employ direct dispatch where possible, and
"hybrid" which makes a dynamic decision based on CPU affinity, ordering,
etc. Routines are implemented to convert between strings and an integer
namespace.

- A new global variable, netisr_dispatch_policy, subsumes existing global
variables for direct dispatch, forced direct dispatch, etc, and is used
for explicit policy interpretation and composition. Old variables remain
so that they can be exported by legacy sysctls for use by old netstat(1)
binaries. A new sysctl and tunable, netisr.dispatch.policy, accepts the
above strings for specifying a global policy default.

- The protocol registration structure, netisr_handler, grows an nh_dispatch
field, which accepts a per-policy policy override. The default value is
'0', which corresponds to "default", meaning that protocols will accept
the global default policy unless otherwise specified.

- Policies are now interpreted and composed explicitly at various points in
packet dispatch; protocol policies override global policies.

- Protocols grow the ability to express a non-opinion about affinity even
when implenting m2cpuid by returning NETISR_CPUID_NONE. In that case, the
framework falls back on source ordering, rather than simply using the
current CPU.

These changes are in support of allowing link layer re-dispatch based on
RSS or similar hashes provided by NICs, especially in the case where the
number of hardware receive queues matches hardware core count, rather than
hardware thread count, requiring further software redistributeon. (i.e.,
on RMI XLR).

MFC after: 3 weeks
Reviewed by: bz
Sponsored by: Juniper Networks, Inc.

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

Changes to support crashdump analysis of netisr:

- Rename the netisr protocol registration array, 'np' to 'netisr_proto',
in order to reduce the chances of symbol name collisions. It remains
statically defined, but it will be looked up by netstat(1).

- Move certain internal structure definitions from netisr.c to
netisr_internal.h so that netstat(1) can find them. They remain
private, and should not be used for any other purpose (for example,
they should not be used by kernel modules, which must instead use the
public interfaces in netisr.h).

- Store a kernel-compiled version of NETISR_MAXPROT in the global variable
netisr_maxprot, and export via a sysctl, so that it is available for use
by netstat(1). This is especially important for crashdump
interpretation, where the size of the workstream structure is determined
by the maximum number of protocols compiled into the kernel.

MFC after: 1 week
Sponsored by: Juniper Networks