QDirListing: make the class move-only

Define both move SMF out-of-line, otherwise MSVC complains that the
private class isn't fully defined at the point of destruction of
std::unique_ptr<QDirListingPrivate>.

Both move SMF are = default'ed; GCC didn't show a warning about this
issue... different implementations, I guess.

"partially-formed" docs boilerplate borrowed from other existing
classes.

Found in API review.

Task-number: QTBUG-125859
Change-Id: I98b57a14bd94e407d9bfafa9ef32cf40c978d7df
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 4e32a45d492fb057cc996efc6791030f3dd525d5)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/io/qdirlisting.cpp

@@ -479,6 +479,24 @@ QDirListing::QDirListing(const QString &path, const QStringList &nameFilters, QD
     d->init();
 }
 
+/*!
+    Move constructor. Moves \a other into this QDirListing.
+
+//! [partially-formed]
+    \note The moved-from object \a other is placed in a partially-formed state,
+    in which the only valid operations are destruction and assignment of a new
+    value.
+//! [partially-formed]
+*/
+QDirListing::QDirListing(QDirListing &&other) = default;
+
+/*!
+    Move-assigns \a other to this QDirListing.
+
+    \include qdirlisting.cpp partially-formed
+*/
+QDirListing &QDirListing::operator=(QDirListing &&other) = default;
+
 /*!
     Destroys the QDirListing.
 */

src/corelib/io/qdirlisting.h

@@ -32,6 +32,9 @@ public:
                 QDir::Filters filters = QDir::NoFilter,
                 IteratorFlags flags = IteratorFlag::NoFlag);
 
+    QDirListing(QDirListing &&);
+    QDirListing &operator=(QDirListing &&);
+
     ~QDirListing();
 
     QString iteratorPath() const;