[lworld] RFR: 8280746: [lworld] Initial core libraries support for value classes

[Mandy Chung]

This is an initial core libraries patch to support value classes; in particular it will get the bootstrap methods for the substitutability test and the default implementation of hashCode to work so that it enables further testing and development to continue.   Only small number of new tests are added in this patch.  More update and new tests will continue via JDK-8280603.

-------------

Commit messages:
 - 8280746: [lworld] Initial core libraries update for value classes

Changes: https://git.openjdk.java.net/valhalla/pull/619/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=619&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280746
  Stats: 177 lines in 30 files changed: 88 ins; 3 del; 86 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/619.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/619/head:pull/619

PR: https://git.openjdk.java.net/valhalla/pull/619