Long term cookie: purge old tokens

https://github.com/marienfressinaud/FreshRSS/issues/465

app/Controllers/indexController.php

@@ -322,7 +322,12 @@ class FreshRSS_index_Controller extends Minz_ActionController {
 	}
 
 	private static function purgeTokens() {
-		//TODO: Delete old token files
+		$oldest = time() - 2629744;	//1 month	//TODO: Use a configuration instead
+		foreach (new DirectoryIterator(DATA_PATH . '/tokens/') as $fileInfo) {
+			if ($fileInfo->getExtension() === 'txt' && $fileInfo->getMTime() < $oldest) {
+				@unlink($fileInfo->getPathname());
+			}
+		}
 	}
 
 	public function formLoginAction () {