dvisvgm needs rebuild to support ghostscript 10

[Karl Berry]

I don't plan to ask for any rebuild of dvisvgm or anything else before
TL23. The work (by all the builders) is not worth the benefit, IMHO.
The users for whom it is critical can either install an older
ghostscript, or install a newer dvisvgm, outside of TL. Admittedly it's
not ideal, but I did not create this drastically gratuitous
incompatibility and am not so interested in spending extra time dealing
with it. Sorry. --best, karl.