[Development] QML instantiation performance

[Juha Vuolle]

> Juha, does that resolve the issues for you?  Gunnar Roth, does that fix the

Yes it does, tests pass on 5.3.1. Big thanks Chris and Matt!

Going back to the original issue I'd need reference from 5.1.1 where
tests won't run, I get same issue as Gunnar:

> file:///data/item.1.qml:3:1: Item is not a type

I believe it is this issue:
https://bugreports.qt-project.org/browse/QTBUG-32078
But I could not find the fix (my guess is that it was going to 5.1.2
but then went to 5.2.0)

Chris I noticed you've reviewed the auto test changes related to that
bug, would happen to know about the fix (I could backport to 5.1.1)?