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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

netgraph/ng_car: Add color marking code

Chained policing should be able to reuse the classification of
traffic. A new mbuf_tag type is defined to handle gereral QoS
marking. A new subtype is defined to track the color marking.

Reviewed by: manpages (bcr), melifaro, kp
Approved by: kp (mentor)
Sponsored by: IKS Service GmbH
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D22110

Fix spelling of "dropped".

Submitted by: Lutz Donnerhacke
Differential Revision: https://reviews.freebsd.org/D23954

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.

sys/netgraph: spelling fixes in comments.

No functional change.

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

- Import the HEAD csup code which is the basis for the cvsmode work.

Add option to set packets per second limits instead of default
bits per second ones.

A node that implements various traffic shaping and rate limiting algorithms.

Approved by: glebius (mentor)