added "memcached" to the Caching driver in according with doctrine/DoctrineBundle#33

liuggio · liuggio · commit 3136fd6c3145 · 2012-06-27T18:12:00.000+03:00
diff --git a/reference/configuration/doctrine.rst b/reference/configuration/doctrine.rst
@@ -251,7 +251,7 @@ certain classes, but those are for very advanced use-cases only.
 Caching Drivers
 ~~~~~~~~~~~~~~~
 
-For the caching drivers you can specify the values "array", "apc", "memcache",
+For the caching drivers you can specify the values "array", "apc", "memcache", "memcached", 
 "xcache" or "service".
 
 The following example shows an overview of the caching configurations:
