We recently removed the integer-based calculation for node widths and heights stored

We recently removed the integer-based calculation for node widths and heights stored
in ND_lw, ND_rw and ND_ht. Unfortunately, dot still does integer-based calculations for
the rank boundaries it stores. This can cause problems in spline routing, since the
(integer) rank values would be used for y for boxes between ranks, but the (double) height
values would be used for the nodes, causing adjacent boxes to have different y values.
The hack added makes sure that boxes returned for nodes use the same integer rounding as dot.