QAppleLogActivity: add a swap() method

Change-Id: Id698d71fbadf5bd0301a346b3216847d0b2f0b54
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/corelib/kernel/qcore_mac_p.h

@@ -293,6 +293,12 @@ public:
         return reinterpret_cast<os_activity_t>(static_cast<void *>(activity));
     }
 
+    void swap(QAppleLogActivity &other)
+    {
+        qSwap(activity, other.activity);
+        qSwap(state, other.state);
+    }
+
 private:
     // Work around API_AVAILABLE not working for templates by using void*
     QAppleOsType<void *> activity;