kangaroo

Copperbox revision 1142.

I've added a separate VDoc type to JoinPrint to represent multi-line documents. This is because horizontal documents track their (horizontal) width. Previously, vertically stacking documents just combined both widths - this was a known bug, but I had rather forgotten about it.

I could track say max width, first width or last width, but none of them seem ideal and seems to make better sense to have a separate multi-line doc type (VDoc) instead. This does change the interface a bit though - previously it was more or less compatible with PPrint.