QtDBus: add member-swap to shared classes

Implemented as in other shared classes (e.g. QPen).

Change-Id: Ic827540b535fc5506165b5395b796a53a00bb096
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/dbus/qdbuspendingcall.cpp

@@ -285,6 +285,14 @@ QDBusPendingCall &QDBusPendingCall::operator=(const QDBusPendingCall &other)
     return *this;
 }
 
+/*!
+    \fn void QDBusPendingCall::swap(QDBusPendingCall &other)
+    \since 5.0
+
+    Swaps this pending call instance with \a other. This function is
+    very fast and never fails.
+*/
+
 /*!
     \fn bool QDBusPendingCallWatcher::isFinished() const
 

src/dbus/qdbuspendingcall.h

@@ -68,6 +68,8 @@ public:
     ~QDBusPendingCall();
     QDBusPendingCall &operator=(const QDBusPendingCall &other);
 
+    void swap(QDBusPendingCall &other) { qSwap(d, other.d); }
+
 #ifndef Q_QDOC
     // pretend that they aren't here
     bool isFinished() const;

src/dbus/qdbusunixfiledescriptor.cpp

@@ -186,6 +186,14 @@ QDBusUnixFileDescriptor::~QDBusUnixFileDescriptor()
 {
 }
 
+/*!
+    \fn void QDBusUnixFileDescriptor::swap(QDBusUnixFileDescriptor &other)
+    \since 5.0
+
+    Swaps this file descriptor instance with \a other. This function
+    is very fast and never fails.
+*/
+
 /*!
     Returns true if this Unix file descriptor is valid. A valid Unix file
     descriptor is not -1.

src/dbus/qdbusunixfiledescriptor.h

@@ -68,6 +68,9 @@ public:
     QDBusUnixFileDescriptor &operator=(const QDBusUnixFileDescriptor &other);
     ~QDBusUnixFileDescriptor();
 
+    void swap(QDBusUnixFileDescriptor &other)
+    { qSwap(d, other.d); }
+
     bool isValid() const;
 
     int fileDescriptor() const;