graphics/wings: update to 2.2.6.1

According to http://www.wings3d.com/?page_id=84 , 2.2.7 is still a
"development release"

https://github.com/dgud/wings/releases/tag/v2.2.6.1
Release Notes:

https://github.com/dgud/wings/blob/349e1668b0b5a4a7464f2f96ef2131a8c4e915bf/README-22.txt