[3dprinter-general] New C++ standard/Qt version requirement for CGAL 6.0

[Joachim Reichel]

Dear maintainers of reverse-dependencies of CGAL,

CGAL 6.0 is planned to be released at the end of the year. This version will 
require C++17 or later. It might be good idea to check already now whether your 
software can be built with that C++ standard version and take appropriate 
actions otherwise.

cloudcompare/gudhi/openems/openscad only: Your package additionally 
build-depends on libcgal-qt5-dev. CGAL will switch to Qt6 in version 6.0 (and 
drop Qt5 support). Does your software also plan to migrate to Qt6, or does it 
support it already?

Best regards,
   Joachim