8214399: Javap -help should provide information about --multi-release option

Reviewed-by: jlahoda

src/jdk.jdeps/share/classes/com/sun/tools/javap/JavapTask.java

@@ -944,7 +944,8 @@ public class JavapTask implements DisassemblerTool.DisassemblerTask, Messages {
         String[] fmOptions = {
             "--module-path", "--system",
             "--class-path", "-classpath", "-cp",
-            "-bootclasspath"
+            "-bootclasspath",
+            "--multi-release"
         };
 
         for (String o: fmOptions) {

src/jdk.jdeps/share/classes/com/sun/tools/javap/resources/javap.properties

@@ -92,6 +92,9 @@ main.opt.system=\
 main.opt.module_path=\
 \  --module-path <path>             Specify where to find application modules
 
+main.opt.multi_release=\
+\  --multi-release <version>        Specify the version to use in multi-release JAR files
+
 main.opt.constants=\
 \  -constants                       Show final constants