Replace public friend operators operator==(), operator!=() of
QNativeIpcKey to friend methods comparesEqual() and
Q_DECLARE_EQUALITY_COMPARABLE macro.
Task-number: QTBUG-120304
Change-Id: If18d86fb18e44f8d2210cba7ca93e4ac478a2a48
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>