RFR: 8254125: Assertion in cppVtables.cpp during builds on 32bit Windows [v2]

[Ioi Lam]

> **Problem:** when iterating over the cloned vtables, the original code assumes that they are laid out consecutively in
>   memory. However, since [JDK-8224509](https://bugs.openjdk.java.net/browse/JDK-8224509), the memory allocated for each
>   of the the cloned vtables is now 8-byte aligned. This introduces gaps between the cloned vtables, and causes the assert
>   to fail.
> 
> **Fix:** the fix is to no longer assume the consecutive memory layout. Instead, use the CppVtables::_index array to
>   access each individual cloned vtable.
> 
> **Note:** I also cleaned up the code significantly. I feel the original code is pretty hard to understand, so if I just
>   do the bare minimum to fix the bug, it will be pretty hard to review.
> 
> I would suggest that the reviewers look at just the new version of the code and see if it's working as described
> (instead of looking at the diff to understand what the bug was and how it has been fixed).
> This version still uses the x-macro CPP_VTABLE_TYPES_DO to enumerate over the classes whose vtables need to be cloned.
> I plan to change that into templates in a future RFE.

Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes
the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last
revision:

 - Fixed more cases with align_up(xxx, SharedSpaceObjectAlignment)
 - Merge branch 'master' into 8254125-cppvtables-assert-on-win32
 - 8254125: Assertion in cppVtables.cpp during builds on 32bit Windows

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/591/files
  - new: https://git.openjdk.java.net/jdk/pull/591/files/addaae99..50dfb2e2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=591&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=591&range=00-01

  Stats: 6758 lines in 165 files changed: 3923 ins; 1067 del; 1768 mod
  Patch: https://git.openjdk.java.net/jdk/pull/591.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/591/head:pull/591

PR: https://git.openjdk.java.net/jdk/pull/591