d/copyright: rewrite from scratch

d/copyright: rewrite from scratch

The d/copyright file was very old and outdated. Create an up to date one
now, also using the recommended semi-machine-readable format.

The following files in the upstream source tree were used to produce
this information:

  COPYING
  xen/COPYING
  xen/include/public/COPYING
  xen/common/COPYING
  xen/common/README.source
  xen/common/libelf/COPYING
  xen/crypto/README.source
  xen/include/crypto/README.source
  docs/README.source
  m4/README.source
  stubdom/vtpm/COPYING
  stubdom/COPYING
  tools/firmware/vgabios/COPYING
  tools/include/xen.COPYING.in
  tools/libacpi/COPYING
  tools/libs/guest/COPYING
  tools/xenmon/COPYING
  tools/libs/stat/COPYING
  tools/xenstore/COPYING

If license text is not available on a Debian system by default, the
included text was copied from files in the upstream LICENSES/ directory.

The 4.17 stable branch was used for this. When we advance the upstream
code to e.g. 4.18 we can check if there have been changes made to these
files and update the large copyright file.

Signed-off-by: Hans van Kranenburg <hans@knorrie.org>