RFR: 8159977: typeof operator does not see lexical bindings declared in other scripts

[Hannes Wallnöfer]

Please review:

Bug: https://bugs.openjdk.java.net/browse/JDK-8159977
Webrev: http://cr.openjdk.java.net/~hannesw/8159977/webrev.00/

A let or const defined global should be visible from other scripts, but only if 
accessed as scope identifier.

Thanks,
Hannes