release readiness

[Lukast dev]

> We've just released the 4th beta, so it's time to check the current state of Krita. We've made some good progress, but I'm not entirely elated, to be honest... We're far from an excellent release yet.

I agree that the state is not very good, I hope to work hard around
Christmas holidays :)

> 262324 lukast.dev at gmail.com krita produces artefacts when upscaling

I'm slowly progressing with this one. TODO is to port scaling to use
new iterators, but
first I need to isolate the actual bug.

We use old iterators still everywhere, and I'm not
sure if we manage to port all code for 2.4 release..

> 217292 boud at valdyas.org Ability to paint transparency masks

I was wondering why is this critical bug? I would classify it as
long-standing wish for feature request..