Fix string leaking (and destructors not getting called) when there are XMLNodes that aren't in the document tree

tinyxml2.h

@@ -264,6 +264,12 @@ public:
         return _allocated;
     }
 
+	void SwapRemove(int i) {
+		TIXMLASSERT(i < _size);
+		_mem[i] = _mem[_size - 1];
+		--_size;
+	}
+
     const T* Mem() const				{
         TIXMLASSERT( _mem );
         return _mem;
@@ -1802,6 +1808,9 @@ public:
     // internal
     char* Identify( char* p, XMLNode** node );
 
+	// internal
+	void MarkInUse(XMLNode*);
+
     virtual XMLNode* ShallowClone( XMLDocument* /*document*/ ) const	{
         return 0;
     }
@@ -1822,6 +1831,13 @@ private:
     int             _errorLineNum;
     char*			_charBuffer;
     int				_parseCurLineNum;
+	// Memory tracking does add some overhead.
+	// However, the code assumes that you don't
+	// have a bunch of unlinked nodes around.
+	// Therefore it takes less memory to track
+	// in the document vs. a linked list in the XMLNode,
+	// and the performance is the same.
+	DynArray<XMLNode*, 10> _unlinked;
 
     MemPoolT< sizeof(XMLElement) >	 _elementPool;
     MemPoolT< sizeof(XMLAttribute) > _attributePool;
@@ -1844,6 +1860,8 @@ inline NodeType* XMLDocument::CreateUnlinkedNode( MemPoolT<PoolElementSize>& poo
     NodeType* returnNode = new (pool.Alloc()) NodeType( this );
     TIXMLASSERT( returnNode );
     returnNode->_memPool = &pool;
+
+	_unlinked.Push(returnNode);
     return returnNode;
 }