MFC r326276:

various: 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.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Adjust the system endian and a.out headers to be more MI and cross-building
friendly. Use the systems headers rather than local versions.

Reviewed by: ru

Fix the type of the NULL arg to execl()

Idea from: Theo de Raadt <deraadt@openbsd.org>

Add support for creating a.out output files in addition to ELF.
This allows booting from compressed binaries using older bootstraps.

Thanks to: dwmalone

$Id$ -> $FreeBSD$

This commit was generated by cvs2svn to compensate for changes in r48905,
which included commits to RCS files with non-trunk default branches.

kgzip is a kzip(8) replacement able to compress and link bootable
32-bit binaries in both ELF and a.out format.

Development sponsored by Global Technology Associates, Inc.

Reviewed/tested by: abial