vl.c: add HMP help to machine The help is based on the actual machine properties exposing only the relevant options. Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com> Reviewed-by: Alexander Graf <agraf@suse.de> Reviewed-by: Greg Bellows <greg.bellows@linaro.org> Message-id: 1418217570-15517-4-git-send-email-marcel.a@redhat.com Signed-off-by: Peter Maydell <peter.maydell@linaro.org>