8075529: Documentation in DocumentationTool.getTask(...) should mention about "null" parameter for doclet

Reviewed-by: jjg

langtools/src/java.compiler/share/classes/javax/tools/DocumentationTool.java

diff --git a/langtools/src/java.compiler/share/classes/javax/tools/DocumentationTool.java b/langtools/src/java.compiler/share/classes/javax/tools/DocumentationTool.java
index 163c2a5..aeb7b98 100644
--- a/langtools/src/java.compiler/share/classes/javax/tools/DocumentationTool.java
+++ b/langtools/src/java.compiler/share/classes/javax/tools/DocumentationTool.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -57,7 +57,7 @@
      * use the tool's default method for reporting diagnostics
      *
      * @param docletClass a class providing the necessary methods required
-     * of a doclet
+     * of a doclet; a value of {@code null} means to use the standard doclet.
      *
      * @param options documentation tool options and doclet options,
      * {@code null} means no options