RFR: 8153652 Update javap to be multi-release jar aware

[Steve Drach]

Hi,

Please review the following changeset that simply supplies the help information for the already existing javap command line option, -multi-release.

webrev: http://cr.openjdk.java.net/~sdrach/8153652/webrev.00/ <http://cr.openjdk.java.net/~sdrach/8153652/webrev.00/>
issue: https://bugs.openjdk.java.net/browse/JDK-8153652 <https://bugs.openjdk.java.net/browse/JDK-8153652>

It turns out that javap forwards unrecognized command line options to the JavaFileManager for processing.  One such option is -multi-release.  The value that the -multi-release option is set to is used by JavaFileManager to open multi-release jar files so that the appropriate versioned view is presented to the client, javap in this case.  All this changeset does is add a help message describing the existing -multi-release command line option. 

The values that can be assigned to this option, and the corresponding multi-release modes that the jar file is configured for are:

9             -> JarFile.Release.VERSION_9
runtime   -> JarFile.Release.RUNTIME
all others -> JarFile.Release.BASE

If the option is not present, the jar file mode is JarFile.Release.Base.

Thanks,
Steve