SimplePie 604 (#2350)

Cherry-pick https://github.com/simplepie/simplepie/pull/604

lib/SimplePie/SimplePie/Cache/File.php

@@ -101,7 +101,7 @@ class SimplePie_Cache_File implements SimplePie_Cache_Base
 	 */
 	public function save($data)
 	{
-		if (file_exists($this->name) && is_writeable($this->name) || file_exists($this->location) && is_writeable($this->location))
+		if (file_exists($this->name) && is_writable($this->name) || file_exists($this->location) && is_writable($this->location))
 		{
 			if ($data instanceof SimplePie)
 			{