Refactor the cyclic reference stack as an object so that we can inject it into the logger constructor rather than having to pass it at every call

Classes/PHPExcel/CalcEngine/CyclicReferenceStack.php

@@ -0,0 +1,58 @@
+<?php
+/**
+ * PHPExcel
+ *
+ * Copyright (c) 2006 - 2012 PHPExcel
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category   PHPExcel
+ * @package    PHPExcel_Calculation
+ * @copyright  Copyright (c) 2006 - 2012 PHPExcel (http://www.codeplex.com/PHPExcel)
+ * @license	http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
+ * @version	##VERSION##, ##DATE##
+ */
+
+
+class PHPExcel_CalcEngine_CyclicReferenceStack {
+
+	private $_stack = array();
+
+
+	public function count() {
+		return count($this->_stack);
+	}
+
+	public function push($value) {
+		$this->_stack[] = $value;
+	}	//	function push()
+
+	public function pop() {
+		return array_pop($this->_stack);
+	}	//	function pop()
+
+	public function onStack($value) {
+		return in_array($value,$this->_stack);
+	}
+
+	public function clear() {
+		$this->_stack = array();
+	}	//	function push()
+
+	public function showStack() {
+		return $this->_stack;
+	}
+
+}	//	class PHPExcel_CalcEngine_CyclicReferenceStack