xatlas wrapper used by Bakery (https://geom.io/bakery/wiki/index.php?title=Bakery_-_GPU_Lightmapper)
This is a simple DLL interface for xatlas: https://github.com/jpcy/xatlas
Additionally it also adds a "singleChart" option to AddUvMesh to allow packing existing UV layouts without re-arranging them.