Update to support Java 16

Support class files with version 60.

Move all use of JDK 15 for testing new features to JDK 16,
leaving JDK 15 not used for testing any more.

Added a test for JDK 16 "Pattern Matching For instanceof"
which is pure javac requiring no desugaring.

Content of README.google:
Name: Java Development Kit (JDK)
URL: https://jdk.java.net/16/
Version: 16.0.2
Revision: NA
License: the GNU General Public License, version 2, with the Classpath Exception.

Description:
This is pulled directly from the website for the JDK releases that has an open source license.
Synlinks have reen resolved using `cp -rL` before uploading.

Fixes: 195025241
Change-Id: I85be8765f71688760f51d5adef8fa626c8e287b3
diff --git a/src/test/examplesJava16/pattern_matching_for_instanceof/Main.java b/src/test/examplesJava16/pattern_matching_for_instanceof/Main.java
new file mode 100644
index 0000000..35a3632
--- /dev/null
+++ b/src/test/examplesJava16/pattern_matching_for_instanceof/Main.java
@@ -0,0 +1,14 @@
+// Copyright (c) 2021, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package pattern_matching_for_instanceof;
+
+final class Main {
+  public static void main(String[] args) {
+    Object obj = "Hello, world!";
+    if (obj instanceof String s) {
+      System.out.println(s);
+    }
+  }
+}