fattened edge has violated otherwise-ok via placement

[growly]

if the edge had not been fattened this via would be legal, but we don't know if the edge needs to be fattened until it is exported to the layout.. why did it get fattened?

[growly]

This problem still exists, but is hard to catch. Two things are going wrong:

1. the line segment that is being fattened is not getting split correctly; fattening will happen around a corner when it needs to and should create a new segment (splitting the polyline) to contain the width increase
2. fattening lines does not consider nearby obstacles because (1) was expected to take care of it (ha)