File format
-----------

#r=radius
	minimum bend radius. Propagates to all subsequent points.
#delta=distance
	maximum distance of line from curve. Propagates to all
	subsequent points.
#tag=name
	name point or shape. Gets passed through 2D->2D transform.
	Affects only the next point.
x-coord y-coord
	line endpoint

#r=, #delta=, and #tag= modify the next point, e.g.,

0 0
#r=2
#tag=foo
1 0
1 1

would set the bend radius at the corner (and the final point) to 2 mm
and the tag of the corner point to "foo".