The inserted subsegments doesn't preserve orientation or the original
segment. This caused problems for me, so I digged down in the code and
found the cause.
The attached patch adds an orientation parameter for new subsegments
and uses it accordingly.

This will give an output where each segment has the same orientation
as the segments in the original PSLG.
An original segment
o----------------->o
might turn into
o------->o------>o
instead of the current possible results:
o<-------o------>o
o<-------o<------o
o------->o<------o

I have used it quite extensively without any problems.
The patch is applied last in the patch series (hopefully i got it right)