sys: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c comment pattern

Remove /^/[*/]\s*\$FreeBSD\$.*\n/

powerpc: clean up empty lines in .c and .h files

sys: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

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.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

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 a floating-point emulator so that a single userland or single ABI
can run on processors that don't have a FPU. This is typically the
case for Book E processors. While a tuned system will probably want
to use soft-float (or use a processor that has a FPU if the usage is
FP intensive enough), allowing hard-float on FPU-less systems gives
great portability and flexibility.

Obtained from: NetBSD