[master] RFR: Only include Mark Word when required [v4]

[Julian Waters]

> WIP, some code here is meant as a placeholder
> 
> Discussion: https://bugs.openjdk.java.net/browse/JDK-8198331
> 
> Current goals and dependencies (To help keep track)
> - [x] 2 bit identity Hash Code
> - [ ] Elimination of locking from the Mark Word entirely (Hopefully)
> - [ ] 5 bit GC section (4 bit object age, 1 bit forwarding state)
> - [ ] No Mark Word in header until required
> - [ ] Support and optimizations for objects guaranteed to not have a Mark Word (May depend on Valhalla for the GC section)

Julian Waters has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Don't initially allocate the Mark Word
 - Initial Commit

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Changes: https://git.openjdk.java.net/lilliput/pull/47/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lilliput&pr=47&range=03
  Stats: 12 lines in 2 files changed: 11 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/lilliput/pull/47.diff
  Fetch: git fetch https://git.openjdk.java.net/lilliput pull/47/head:pull/47

PR: https://git.openjdk.java.net/lilliput/pull/47