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

o Allow btxld to be compiled on 64-bit machines
o s/unsigned/unsigned int/g
o Add -Wall

btxld can now be built as a cross-tool for cross-building i386/pc98 on
platforms that don't have btxld (such as alpha).

$Id$ -> $FreeBSD$

This commit was generated by cvs2svn to compensate for changes in r39092,
which included commits to RCS files with non-trunk default branches.

btxld is a link editor for BTX (boot extender) clients, supporting ELF,
a.out, and binary formats.