[Patch] Support for Qt6

[rkatzmann]

I have tried to build on Ubuntu 22.04 with Qt5, but it was failing.
A few days later I found out that it was because package-naming was not straight-forward.

Meanwhile I ported EbnfStudio + GuiTools to Qt6, but have done not much of testing except loading one EBNF file.
Originally I thought EbnfStudio is for Qt6, because it's not mentioned that it required older Qt5.

ebnfstudio-master.patch.txt
guitools-master.patch.txt

[rochus-keller]

Well, when I implemented most of my tools there was no Qt6; and actually I'm not interested in Qt6, but switched to LeanQt and LeanCreator (see https://github.com/rochus-keller/LeanQt and https://github.com/rochus-keller/LeanCreator/).

Thanks for the diffs; I had a brief look at them; looks as if QTC (once more) made breaking changes with no but cosmetic reasons. I recommend to use LeanQt to compile the tool instead. A BUSY file is available. Also note that the code is in C++98; if your compiler happens to default to another standard, please add the "-std=c++98" cflag; I should update my BUSY file accordingly.