[Development] Use of Standard Library containers in Qt source code

[Edward Welbourne]

Thanks to Olivier for pointing out a mistake:

> I've fixed issues in qmake [0] where for-loops caused similar problems.
> [0] e.g. https://codereview.qt-project.org/#/c/161133

That should have been:
[0] https://codereview.qt-project.org#/c/141305/14//ALL,unified

        Eddy.