RFR: 8141564: Convert TraceItables and PrintVtables to Unified Logging

[Rachel Protacio]

Hi,

Please review this changeset that converts -XX:+TraceItables and 
-XX:+PrintVtables flags to -Xlog:itables and -Xlog:vtables.

Open webrev: http://cr.openjdk.java.net/~rprotacio/8141564/
Bug: https://bugs.openjdk.java.net/browse/JDK-8141564

In case it's not clear, the changes in oops/klassVtable.cpp around 
462-498 are a refactoring of the duplicate code from a conditional to a 
function with a boolean argument.

Thank you,
Rachel