RFR (XS): 8160647: [JVMCI] need to be able to copy internal arrays from LocalVariableTable and LineNumberTable

[Doug Simon]

Existing JVMCI clients create modified LocalVariableTable and LineNumberTable objects from existing ones. To support this, (copies of) these object's internals must be accessible. The fix for JDK-8159613 removed such access and this bug restores it.

https://bugs.openjdk.java.net/browse/JDK-8160647
http://cr.openjdk.java.net/~dnsimon/8160647/

-Doug