update twig to 2.9

tools/rebuild.php

@@ -42,7 +42,7 @@ if(!$options['quiet'])
 	echo "Clearing template cache...\n";
 
 load_twig();
-$twig->clearCacheFiles();
+$twig->getCache()->clear();
 
 if(!$options['quiet'])
 	echo "Regenerating theme files...\n";