Review request JDK-8007629 Remove extraneous quit from shell.js

[Jim Laskey (Oracle)]

Please review http://cr.openjdk.java.net/~jlaskey/8007629/webrev.00/index.html

This solidifies quit and exit has always being available.  quit is an alias for exit.  Both accept an exit code.  The assumption is that quit() will primarily be used for interactive sessions and that exit(0) will be used for shell scripting.

Tests will follow with a more comprehensive shell scripting test bed.