qapi: Implement deprecated-output=hide for QMP event data

This policy suppresses deprecated bits in output, and thus permits
"testing the future".  Implement it for QMP event data: suppress
deprecated members.

No QMP event data is deprecated right now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210318155519.1224118-6-armbru@redhat.com>
4 files changed