l3backend: adding new DVI specials?

[Karl Berry]

    A "latex" run *cannot* know what the driver is unless it's told: you 

Yes, of course.

    The graphics package has for years assumed no option -> dvips, and 

Yes, and that is good.

    dvipdfmx users are thus accustomed to having to specify it. 

Right. Ditto dvisvgm, etc. So, don't output the header= \special unless
either no option is given, or dvips is explicitly given.
What am I missing? Sorry ... -k