Release Note: JShell -- New tool and API for interactive Java

Provide an interactive tool to evaluate declarations, statements, and expressions of the Java programming language, together with an API so that other applications can leverage this functionality. Adds Read-Eval-Print Loop (REPL) functionality for Java.

The `jshell` tool accepts "snippets" of Java code, evaluating them and immediately displaying the results. Snippets include variable and method declarations without enclosing class. An expression snippet immediately shows its value. The `jshell` tool also accepts commands for displaying and controlling snippets.

The `jshell` tool is built on the JShell API, making the evaluation of snippets of Java code available any Java program.

See:
  - [`jshell` tool User's Guide](http://docs.oracle.com/javase/9/jshell/toc.htm)
  - [`jshell` tool Reference](https://docs.oracle.com/javase/9/tools/jshell.htm)
  - [JShell API Specification](http://download.java.net/java/jdk9/docs/api/jdk/jshell/package-summary.html)
  - [JShell module specification](http://download.java.net/java/jdk9/docs/api/jdk.jshell-summary.html)