RFR 8098847: obj."prop" and obj.'prop' should result in SyntaxError

[A. Sundararajan]

Please review http://cr.openjdk.java.net/~sundar/8098847/ for 
https://bugs.openjdk.java.net/browse/JDK-8098847

PS. This is one of the issues reported in 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2015-June/004776.html

Thanks,
-Sundar