[dvipdfmx] dvipdfmx: wrong exit status

[Shunsaku Hirata]

>     Dvipdfmx ignores image files which do not exist and tries to
>     continue processing.
>
> Seems like it would be better to exit with bad status in this case?
> The output cannot be as the user expected. -k

I think this is the same behavior as dvipdfm and also as dvips.
I don't know why but there must be a reason for choosing
such behavior.

If there are not so many practical benefits I'd rather choose
leaving this unchanged.

Thanks,
Shunsaku Hirata