sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

sys/dev: further 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.

Remove pc98 support completely.
I thank all developers and contributors for pc98.

Relnotes: yes

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.

Replace explicit calls to video methods with their respective variants
implemented with macros. This patch improves code readability. Reasoning
behind vidd_* is a sort of "video discipline".

List of macros is supposed to be complete--all methods of video_switch
ought to have their respective macros from now on.

Functionally, this code should be no-op. My intention is to leave current
behaviour of touched code as is.

No objections: rwatson
Silence on: freebsd-current@
Approved by: cognet

Use the clear function provided by the video adapter driver.

Submitted by: chi@bd.mbn.or.jp (Chiharu Shibata)

Add new graphical screen saver (dragon_saver).
Add support for NEC PC-9821 PEGC screen (fire/logo/rain/warp_saver).