ENH: add UPtrList swap() method

src/OpenFOAM/containers/Lists/UPtrList/UPtrList.H

@@ -169,6 +169,9 @@ public:
             //- Return true if the UPtrList is empty (ie, size() is zero)
             inline bool empty() const;
 
+            //- Swap content with another UPtrList
+            inline void swap(UPtrList<T>& lst);
+
             //- Return reference to the first element of the list
             inline T& first();
 

src/OpenFOAM/containers/Lists/UPtrList/UPtrListI.H

@@ -39,6 +39,13 @@ inline bool Foam::UPtrList<T>::empty() const
 }
 
 
+template<class T>
+inline void Foam::UPtrList<T>::swap(UPtrList<T>& lst)
+{
+    ptrs_.swap(lst.ptrs_);
+}
+
+
 template<class T>
 inline T& Foam::UPtrList<T>::first()
 {