QCollator(SortKey): add member-swap

This is required for a Qt value type these days.

Change-Id: Ibd4e1581a4f4791a410caa10fede92c26b35dd9d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qcollator.cpp

@@ -117,6 +117,13 @@ QCollator &QCollator::operator=(const QCollator &other)
     return *this;
 }
 
+/*!
+    \fn void QCollator::swap(QCollator &other)
+
+    Swaps this collator with \a other. This function is very fast and
+    never fails.
+*/
+
 /*!
     \internal
  */

src/corelib/tools/qcollator.h

@@ -61,8 +61,10 @@ public:
     QCollatorSortKey &operator=(const QCollatorSortKey &other);
 #ifdef Q_COMPILER_RVALUE_REFS
     inline QCollatorSortKey &operator=(QCollatorSortKey &&other)
-    { qSwap(d, other.d); return *this; }
+    { swap(other); return *this; }
 #endif
+    void swap(QCollatorSortKey &other)
+    { d.swap(other.d); }
 
     bool operator<(const QCollatorSortKey &key) const;
     int compare(const QCollatorSortKey &key) const;
@@ -84,6 +86,9 @@ public:
     ~QCollator();
     QCollator &operator=(const QCollator &);
 
+    void swap(QCollator &other)
+    { qSwap(d, other.d); }
+
     void setLocale(const QLocale &locale);
     QLocale locale() const;