RFR: Add two missing weak roots sets

[Stefan Karlsson]

Hi all,

Please review this patch to add two missing weak roots sets

http://cr.openjdk.java.net/~stefank/zgc/zMissingWeakRoots/webrev.01/

The JvmtiExport::weak_oops_do call was moved in the upstream repository, 
and TRACE_WEAK_OOPS_DO was recently introduced for the Trace API.

This was found while testing some jdi tests that used the JvmtiTagMap.

Thanks,
StefanK