gEDA-dev: polygon crash

[DJ Delorie]

I'm starting to see polygon bugs again, while putting together a
fairly complex ground plane.  The symptom is that it gets into an
infinite recursion of sorts, with r_NoHolesPolygonDicer calling itself
over and over again.  It looks like it's always got a different
pointer passed to it, but the stack is definitely blowing up due to
the nesting.

The only unusual thing I'm doing is using a negative keep-away to make
cuts in the ground plane under my crystals (4u line, -1u keepaway).

Anyone want to work on this one?