qapi: Generate up-to-date copyright notice

qapi: Generate up-to-date copyright notice

Each generator carries a copyright notice for the generator itself,
and another one for the files it generates.  Only the former have been
updated along the way, the latter have not, and are all out of date.

Fix by copying the generator's copyright notice to the generated files
instead.  Note that the fix doesn't copy the "Authors:" part; the
generated files' outdated Authors list goes away without replacement.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180211093607.27351-4-armbru@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
[eblake: Flatten each 'blurb' to one line]
Signed-off-by: Eric Blake <eblake@redhat.com>