This can only be completed in Qt 7, due to BC guarantees. I've only
updated the source code for QHostAddress and its unit test and even then
I did not touch the documentation. This needs to be completed in Qt 7.0
Change-Id: I26b8286f61534f88b649fffd166b695882f8f3b5
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>