RFR (S) 8182397: Race in field updates when creating ArrayKlasses can lead to crash

[coleen.phillimore at oracle.com]

Summary: Update array_klass field in component mirror after 
klass.java_mirror field for concurrent readers in compiled code.

See bug for details.

open webrev at http://cr.openjdk.java.net/~coleenp/8182397.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8182397

Ran tier1 testing with -Xcomp and without.  Thank you to Tom for the 
test and diagnosis.

Thanks,
Coleen