QCollator(SortKey): declare as shared

This enables specialisations of (std and q) swap using member-swap
and declares the types movable for efficient use in Qt containers,
and QList in particular.

This is a binary-incompatible change, so cannot wait for 5.2.1.

Change-Id: I7e90b6397ac4d00d0a7a5c42bae166c1b43e1994
Reviewed-by: Aleix Pol Gonzalez <aleixpol@kde.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qcollator.h

@@ -122,6 +122,9 @@ private:
     void detach();
 };
 
+Q_DECLARE_SHARED(QCollatorSortKey)
+Q_DECLARE_SHARED(QCollator)
+
 QT_END_NAMESPACE
 
 #endif // QCOLLATOR_P_H