[Development] "adjust to qt_plugin.prf changes", submit policy

[Oswald Buddenhagen]

moin,

i posted such changes to several modules.
to my dismay, some maintainers have already approved *and staged/submitted*
these changes without being asked to, thus breaking things (because these
changes depend on pending qtbase changes).
i don't know how many more times i need to repeat this: as the reviewer,
*don't* hit the submit/stage button unless asked to (or you can be
reasonably sure that the contributor wants you to do this, which is
typically the case for non-reviewers).