RFR: 8114827: JDK 9 multi-release enabled jar tool

[Steve Drach]

Hi,

Please review the following changeset that makes it easier to create multi-release jar files with jar tool.  

webrev: http://cr.openjdk.java.net/~sdrach/8114827/webrev.01/
issue: https://bugs.openjdk.java.net/browse/JDK-8114827

The changeset is the implementation of a new command line option, —release n, that indicates all following files and directories are placed in the META-INF/versions/n directory of a multi-release jar file.  The new command line syntax is

jar [OPTION...] [ [--release VERSION] [-C dir] files] …

An example is

jar --create --file mr.jar README -C foo classes --release 9 -C foo9 classes Foo.class

This will put README and all the files under foo/classes in the base (or root) directory of a jar file and put Foo.class and all the files under foo9/classes in the META-INF/versions/9 directory of the jar file.