Blender Git Loki

Fix part of T44320 selecting islands can fail.

Issue here is simple and has been fixed in other places such as
texpainting: Basically if face has different winding, do not calculate
it as adjucent to the other face, even if UV is identical.

This allows us to stack islands of symmetrical closed meshes on top of
one another and still be able to select the two identical island halfs
(provided the normals are correct of course).