Use QT6_{DECL,CALL}_NEW_OVERLOAD mechanism to provide new constexpr overloads for isNull(), variant(), and version(). Move the old methods into removed_api.cpp Use this as an opportunity to optimize the implementaiton of the methods. Also add compile-time checks to the tests. It turns out that QNX compiler fails to compile the default QUuid::isNull() implementation in constexpr context, so rewrite it using a loop. Change-Id: Ia23c81194ea27b369f00ce73b016695600187e46 Reviewed-by: Marc Mutz <marc.mutz@qt.io> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>