Like with the QLine(F) case, we have to use QT_CORE_REMOVED_SINCE to
remove the old member operators, but also need to guard the new friend
functions with !(QT_CORE_REMOVED_SINCE), because QEasingCurve is also
one of the core types, and on Windows the metatype interface for it is
instantiated in removed_api.cpp.
Task-number: QTBUG-120308
Change-Id: I1bd66f7230afd3eba868d05fd496ab13a0331178
Reviewed-by: Tatiana Borisova <tatiana.borisova@qt.io>
a4341827ac