Comment 7 for bug 699318

Fine. First I fixed rounding, then I removed rounding :-) Both commits directly on master, as per DJ's request.

I removed rounding, because it was for display, only, so the number of distinct drills on display and in the actual CNC file could differ. Very confusing. Now the Gerber fab file can show more than one drill of the same size, if they differ less than one digit. Hopefully less confusing, at least less fooling the user.

One can always apply a vendor drill map, joining similar drill sizes for all, display as well as CNC files.