add copyright

Author: parrt

runtime/Java/src/org/antlr/v4/runtime/tree/xpath/XPathLexer.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) 2012-2016 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
 package org.antlr.v4.runtime.tree.xpath;
 
 import org.antlr.v4.runtime.CharStream;