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

Apply style(9) and unbreak build.

This went unnoticed during the WARNS bump, as this tool is not connected
to the build.

Add support for selecting from multiple tuners.

Suggested by: usleepless <usleepless@gmail.com>

Tidy up forrmat. No functional changes.

Change formatting to be more compliant with style(9). Doubtless
others will find more things to change.

Change copyright notice to the FreeBSD 2 clause notice.

Approved by: John Wehle <john\@feith.com>

Set channel utility for Hauuapuge PVR-250 and PVR-350.

This s part of an import of the PVR-250 driver. Originally it was
calleed pvr250-setchannel, but it seems better to improve this program
to work for any tuner card, so I'm starting with a more generic name.
That shouldn't mislead anybody: currently the program only works with
the (yet to be committed) cxm driver.

Contributed by: John Wehle <john\@feith.com>