Replace remnants of TQtC-licensed code

[T-640]

Hello!

I want to statically link my commercial program with QtAutoUpdater. Given that this library is BSD-licensed this is acceptable. However, there are remnants of code borrowed from the earlier version of Qt Installer Framework in "adminauthoriser_" files. Their code is dual-licensed under LGPL or commercial license. As far as I understand this practically means that despite your work being BSD-licensed I am not allowed to link statically to it unless I pay The Qt Company a huge sum of money, which is an overkill for something as trivial as static linking to this particular library.

Could you rewrite the "contaminated" code please? It would seem it has already been done partially, at least in the Linux version of admin authorization, although I am not sure about the "qt_create_commandline" function (was it borrowed from QProcess API?).

Are there any other parts not licensed under BSD?