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

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

spdx: The BSD-2-Clause-NetBSD identifier is obsolete, drop -NetBSD

The SPDX folks have obsoleted the BSD-2-Clause-NetBSD 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/arm: 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.

Use the MD __size_t to avoid a dependency on/include of non-MD header files.

This should fix the compilation of the lua 5.3.4 port, among others.

Reported by: Russell Haley <russ.haley@gmail.com>

Preserve VFP state across signal delivery.

We don't have enouch space to store full VFP context within mcontext
stucture. Due to this:
- follow i386/amd64 way and store VFP state outside of the mcontext_t
but point to it. Use the size of VFP state structure as an 'magic'
indicator of the saved VFP state presence.
- teach set_mcontext() about this external storage.
- for signal delivery, store VFP state to expanded 'struct sigframe'.

Submited by: Andrew Gierth (initial version)
PR: 217611
MFC after: 2 weeks

Cleanup structures related to VFP and/or mcontext_t.
- in mcontext_t, rename newer used 'union __vfp' to equaly sized 'mc_spare'.
Space allocated by 'union __vfp' is too small and cannot hold full
VFP context.
- move structures defined in fp.h to more appropriate headers.
- remove all unused VFP structures.

MFC after: 2 weeks

Remove NetBSD implementation details not relevant to FreeBSD.

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

The NetBSD Foundation has granted permission to remove clauses 3 and 4.

Obtained from: NetBSD

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

Import FreeBSD/arm kernel bits.
It only supports sa1110 (on simics) right now, but xscale support should come
soon.
Some of the initial work has been provided by :
Stephane Potvin <sepotvin at videotron.ca>
Most of this comes from NetBSD.

We need machine/{signal,ucontext}.h to build a cross GCC compiler.
So craft the proper versions of these and commit em.