Cache: is_supported

1. Cache_redis: Standardize the style as other driver.
2. Cache_wincache:  Also check wincache.ucenabled
diff --git a/system/libraries/Cache/drivers/Cache_wincache.php b/system/libraries/Cache/drivers/Cache_wincache.php
index 528b2b9..9cc6ff0 100644
--- a/system/libraries/Cache/drivers/Cache_wincache.php
+++ b/system/libraries/Cache/drivers/Cache_wincache.php
@@ -194,7 +194,7 @@
 	 */
 	public function is_supported()
 	{
-		if ( ! extension_loaded('wincache'))
+		if ( ! extension_loaded('wincache') OR ! ini_get('wincache.ucenabled'))
 		{
 			log_message('debug', 'The Wincache PHP extension must be loaded to use Wincache Cache.');
 			return FALSE;