Regression: shapefile export for unclosed polygon
Regression: shapefile export for unclosed polygon

polygons were given unclosed vertex lists in
0df6acde9bb309d865991b05cc15a301337cc5d5, but the shapefile writer wasn't
updated. This was missed in my local tests because testdata aren't recreated if
they exist. Travis found it, because it rebuilds the test shapefiles every run.

There's a lesson in this somewhere.

fortyninemaps/karta,fortyninemaps/karta,fortyninemaps/karta