[8u20] 8044695: __stack__ becomes visible in Error properties

[A. Sundararajan]

Please approve - copying jdk9 reviewers as I had to manually apply the 
diff on NativeError.java.

Bug: https://bugs.openjdk.java.net/browse/JDK-8044695
jdk9 webrev: http://cr.openjdk.java.net/~sundar/8044695/webrev.00/
jdk8u-dev webrev: 
http://cr.openjdk.java.net/~sundar/8044695/8u-dev/webrev.00/
jdk9 review thread: 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2014-June/003053.html
jdk9 changeset: http://hg.openjdk.java.net/jdk9/dev/nashorn/rev/1987caf5e034

Thanks
-Sundar