Bugfix: (manual merge from a pull request from amironov) Work item GH-82 - PHPExcel_Worksheet::getCellCollection() may not return last cached cell

Classes/PHPExcel/CachedObjectStorage/Memory.php

@@ -35,6 +35,14 @@
  */
 class PHPExcel_CachedObjectStorage_Memory extends PHPExcel_CachedObjectStorage_CacheBase implements PHPExcel_CachedObjectStorage_ICache {
 
+    /**
+     * Dummy method callable from CacheBase, but unused by Memory cache
+     *
+	 * @return	void
+     */
+	protected function _storeData() {
+	}	//	function _storeData()
+
     /**
      * Add or Update a cell in cache identified by coordinate address
      *