Asymptote Extent calculation of boxes doesn't take into account linewidth

[rocky]

This can be seen in the Dice example in the middle Dice

$ ./doc2latex.py -c Examples -s Dice
...
$ make mathics.pdf
...
(./mathics.mtc1) (/usr/share/texmf/tex/latex/lm/t1lmtt.fd)
Overfull \hbox (18.52664pt too wide) in paragraph at lines 119--119
...