lena.png and lena.jpg are provided in original upstream examples
but are a photo of Lena (Söderberg) Forsén that is not free
(lintian warning license-problem-non-free-img-lenna,
https://en.wikipedia.org/wiki/Lena_Forsén)

We therefore replace the non-free image files with the debian logo,
openlogo-100.jpg and openlogo-100.png
from https://www.debian.org/logos/
to use with the examples.

See also debian/patches/example_image_free.patch

