Since 'hax' is a possible accelerator nowadays, too, the '-accel'
option should support it and we should mention this accelerator
in the documentation, too.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1493875481-16388-1-git-send-email-thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>