Review Request: JDK-8168836 Minor clean up on warning/error messages on --add-exports and --add-reads

[David Holmes]

Hi Mandy,


>
> http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8168836/webrev.00/
>
> This patch improves the warning/error message to include the option name, emit a warning if unknown module is specified with —-patch-module be consistent with the options.
>
> Mandy

As a result of this change we now reject an empty classpath with an error:

  /java/re/jdk/9/promoted/all/150/binaries/linux-x64/bin/java -cp "" Hello
Error: -cp requires class path specification

was that intentional? We've accepted an empty -cp value for a very long 
time.

Thanks,
David