It's not actually exercised by anything in our source tree, but is
potentially useful and has been part of the documented public API for
some time. So mention that the caller is responsible for delete[]ing
its return and add a test that exercises it.
Task-number: QTPM-1385
Change-Id: Ifc5284b9eb1b678cf3c9708c681311e874838fc6
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>
