Version 2.19.0.

Hi Jonathan, I've just synced up the GH master, release and testing branches to gitlab, including your most recent fix-knob-crasher MR, and I'm ready to finally release this as 2.19.0 proper now. Which is what this MR is about (it's just a version bump). Note that I already released 2.18.0 and 2.18.1 last week, so the bump goes to 2.19.0 instead. Which looks a bit odd, since those earlier bumps to 2.18.x aren't in any of the current branches any more, but hey, we're advancing by leaps and bounds 😄, and this will let me keep those earlier releases which is a good thing IMHO.