Copperbox revision 2181.
I've changed drawing to work with contextual units - that is units that potentially have access to the current font size. This means I should be able to define em and en for example that are scaling factors of Point size rather than regular scalar units like PostScript point or centimeter.
This is just the first round of work, I haven't yet looked at displacement or what to do about answer types (e.g the bounding boxes returned by a PosGraphic).
