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

Find places to store the previously implicityly passed unit number in
the three configuration ioctls which need a unit number.

Add a "ccd.ctl" device for config operations.

Implement ioctls on ccd.ctl which rely on the explicityly passed
unit numbers.

Update ccdconfig to use the new ccd.ctl interface.

Add code to the kernel to detect old ccdconfig binaries, and whine
about it.

Add code to ccdconfig to detect old kernels, and whine about it.

These two compatibility measures will be retained only for a limited
period since they are in the way of GEOM'ification of ccd.

This commit was generated by cvs2svn to compensate for changes in r13047,
which included commits to RCS files with non-trunk default branches.

Oops, forgot pathnames.h.