Update to millipixels 0.17.0.
This forks Megapixels to Millipixels, because we agreed not to make a special effort to track upstream, and now Millipixels is more of a L5-specific project. Megapixels is still in Debian, so that warranted a name change to avoid packaging conflicts.
Draft because this needs to go in sync with Librem5/linux-next!430 (closed) Please review regardless of the draft status! It's there to prevent accidents with merging.
It can be installed alongside Megapixels, so there's no need to put off merging.