* Removes dependency on QtX11Extras and implements placeholder solution with QtGUI private API
* Fixes CMakeLists.txt to work with Qt5 and Qt6
* Removes all other uses of X11extras
* Renames and moves x11 methods into ads::internal
* Fixes typo
* Adds gui-private to src.pro
macOS is identified as UNIX by CMake, but Qt doesn't actually use X11
there (and X11 support is not available by default anyway). Change the
condition that includes X11Extras to if (UNIX AND NOT APPLE) instead of
just if (UNIX) to mitigate that. This makes the build on macOS work
with CMake.
Co-authored-by: Christian Seiler <c.seiler@luxflux.de>
