Issue #5032 - Fixing License and javadoc

Signed-off-by: Joakim Erdfelt <joakim.erdfelt@gmail.com>

jetty-servlet/src/main/java/org/eclipse/jetty/servlet/DebugServletMetricsListener.java

@@ -1,10 +1,31 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
 package org.eclipse.jetty.servlet;
 
 import org.eclipse.jetty.server.Request;
 import org.eclipse.jetty.servlet.listener.ServletMetricsListener;
 import org.eclipse.jetty.util.log.Log;
 import org.eclipse.jetty.util.log.Logger;
 
+/**
+ * A Debug Logging {@link ServletMetricsListener}.
+ */
 public class DebugServletMetricsListener implements ServletMetricsListener
 {
     protected final Logger logger;