Detect if bootclasspath/classpath is set in module mode

[Alan Bateman]

Mandy Chung wrote:
> Karen, Alan,
>
> We don't support bootclasspath and classpath  in module mode.  I added 
> the check in hotspot and java launcher.  Can you review this simple fix?
>
> Webrev at:
>   http://cr.openjdk.java.net/~mchung/jigsaw/modular-mode-checks/
>
> Thanks
> Mandy
Looks okay to me. A minor comment is that "is_modules_mode" might be a 
bit better than "is_modular_mode".

-Alan.