[foreign] RFR 8211063: StdLibTest improvements

[Sundararajan Athijegannathan]

Please review.

Bug: https://bugs.openjdk.java.net/browse/JDK-8211063
Webrev: http://cr.openjdk.java.net/~sundar/8211063/webrev.00/

This patch is a contribution from Jorn Vernee [1]. It has been tested on 
Mac and Linux (by me & Maurizio)

[1] 
http://mail.openjdk.java.net/pipermail/panama-dev/2018-September/002773.html

Thanks,
-Sundar