qt 5.4.0

Just doing some testing for #34876. Abusing the fact the bot can compile quicker than my laptop can a lot of the time, heh.
Ah, alright. Let me take one last crack at this. I want to try the last remaining upstream suggestion, so that when upstream turn around and go *"Well, did you try x?"* I can go *yup*. Failing that, I'll cull back all my unnecessary/now defunct changes here.