[foreign] RFR 8212920 : Tweak StructByValueTest to verify for by-value semantics.

[Jorn Vernee]

Hello,

I'd like to contribute a patch that tweaks StructByValueTest to verify 
that by-value semantics are being followed. It turns out that this 
wasn't the case, and a bug snuck into my windows binder changes like 
that.

I'm also doing this to test out the workflow now that I'm an author, so 
any comments in that field (e.g. about the JBS bug I've made) are 
welcome as well :)

As a reminder, I'm not a committer, so someone else will have to push 
this.

Bug : https://bugs.openjdk.java.net/browse/JDK-8212920
Webrev : 
http://cr.openjdk.java.net/~jvernee/panama/webrevs/8212920/webrev.00/

Thanks,
Jorn