HashSet and PackedList get an unset() method

- provides a convenient (and lazy) means of removing entries

src/OpenFOAM/containers/HashTables/HashSet/HashSet.H

@@ -136,6 +136,12 @@ public:
             return insert(lst);
         }
 
+        //- Unset the specified key - same as erase
+        bool unset(const Key& key)
+        {
+            return HashTable<nil, Key, Hash>::erase(key);
+        }
+
 
     // Member Operators
 

src/OpenFOAM/containers/Lists/PackedList/PackedList.H

@@ -201,6 +201,10 @@ public:
         //  Default value set is the max_value.
         inline bool set(const label, const unsigned int val = ~0u);
 
+        //- Unset the entry at index I. Return true if value changed.
+        //  Never auto-vivify entries.
+        inline bool unset(const label);
+
         //- Return the underlying packed storage
         inline List<unsigned int>& storage();
 
@@ -240,6 +244,8 @@ public:
 
         //- Reserve allocation space for at least this size.
         //  Never shrinks the allocated size.
+        //  The list size is adjusted as per DynamicList with
+        //  SizeInc=0, SizeMult=2, SizeDiv=1
         inline void reserve(const label);
 
         //- Clear the list, i.e. set addressable size to zero.
@@ -249,7 +255,7 @@ public:
         //- Clear the list and delete storage.
         inline void clearStorage();
 
-        //- Shrink the allocated space to what is used.
+        //- Shrink the allocated space to what is actually used.
         inline void shrink();
 
         //- Transfer the contents of the argument list into this list

src/OpenFOAM/containers/Lists/PackedList/PackedListI.H

@@ -810,6 +810,19 @@ inline bool Foam::PackedList<nBits>::set
 }
 
 
+template<unsigned nBits>
+inline bool Foam::PackedList<nBits>::unset(const label i)
+{
+    // lazy - ignore out-of-bounds
+    if (i < 0 || i >= size_)
+    {
+        return false;
+    }
+
+    return iteratorBase(this, i).set(0u);
+}
+
+
 template<unsigned nBits>
 inline void Foam::PackedList<nBits>::append(const unsigned int val)
 {