qapi: Remove dead visitor code Commit cbc95538 removed unused start_handle() and end_handle(), but forgot to remove their declarations. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1447836791-369-19-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>