[8u20] approval request for 8027933: Add --const-as-var option

[A. Sundararajan]

Hi,

Please approve jdk8u20 backport of fix for  8027933: Add --const-as-var 
option

Backported from jdk9 with no changes. Patch applied "as is".

Bug: https://bugs.openjdk.java.net/browse/JDK-8027933
Webrev: http://cr.openjdk.java.net/~sundar/8027933/
jdk9 review thread : 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2014-May/002938.html

Thanks,
-Sundar