[Development] QList for Qt 6

[Edward Welbourne]

NIkolai Marchenko (24 May 2019 12:03) asked
> Is the gordian knot of full SC really possible to unravel or is it time to axe it?

Or at least, for this one case, recognise that a SC break is better than
the alternatives and, since this is the Qt6 transition where we don't
promise not to make SC breaks, bite the bullet.  If we recommend
changing QList to QVector (or auto, where applicable) and give
guidelines on what kinds of code patterns to watch out for, where some
other change may be needed, there's a straightforward task with clear
guidance on where to expect to complications.  Any client code whose
maintainers do code review will then have one big sweeping change and
then put QList behind them.

	Eddy.