Release the cumulation buffer after firing upstream so we don't end up

with a "leak" because of a very big ChannelBuffer. This patch is
extracted of the pull request 39. Thanks to arya for the patch

src/main/java/org/jboss/netty/handler/codec/frame/FrameDecoder.java

@@ -298,6 +298,10 @@ public abstract class FrameDecoder extends SimpleChannelUpstreamHandler {
 
             unfoldAndFireMessageReceived(context, remoteAddress, frame);
         }
+
+        if (!cumulation.readable()) {
+          this.cumulation = null;
+        }
     }
 
     private void unfoldAndFireMessageReceived(ChannelHandlerContext context, SocketAddress remoteAddress, Object result) {