RFR: 8224509: Incorrect alignment in CDS related allocation code on 32-bit platforms

[Calvin Cheung]

CDS aligns pointers and sizes to BytesPerWord. On 64-bit, BytesPerWord = 8. On 32-bit, BytesPerWord = 4.

To make the alignment consistent between 64- and 32-bit platforms, this patch changes the alignment value to 8.

Testing: tiers 1 - 4
               built linux-x86-debug.

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Commit messages:
 - 8224509 (initial commit)

Changes: https://git.openjdk.java.net/jdk/pull/476/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=476&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8224509
  Stats: 12 lines in 5 files changed: 3 ins; 1 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/476.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/476/head:pull/476

PR: https://git.openjdk.java.net/jdk/pull/476