[master] RFR: 8347710: [Lilliput] Implement 4 byte headers [v7]

[Roman Kennke]

> Packs/reduces header bits to just 4 bytes.
> 
> This reduces the number of Klass* bits to 19 bits, which allows for ~500,000 classes.
> 
> Testing:
> 
> - tier1 (-UCOH)
> - tier2 (-UCOH)
> - tier1 (+UCOH)
> - tier2 (+UCOH)

Roman Kennke has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 13 commits:

 - Merge remote-tracking branch 'origin/master' into JDK-8347710
 - Comment-out unimplemented RISCV parts
 - Fix CompressedClassPointersEncodingScheme.java
 - Remove some override that cause build failures
 - Fix 32 bit build
 - Merge branch 'JDK-8320761' into JDK-8347710
 - Cast size_t to int
 - Merge branch 'JDK-8320761' into JDK-8347710
 - Merge branch 'JDK-8346011' into JDK-8320761
 - Make all constants constexpr
 - ... and 3 more: https://git.openjdk.org/lilliput/compare/33f69df3...b4b3e4f7

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

Changes: https://git.openjdk.org/lilliput/pull/193/files
  Webrev: https://webrevs.openjdk.org/?repo=lilliput&pr=193&range=06
  Stats: 861 lines in 71 files changed: 109 ins; 620 del; 132 mod
  Patch: https://git.openjdk.org/lilliput/pull/193.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/193/head:pull/193

PR: https://git.openjdk.org/lilliput/pull/193