[lworld] RFR: [lworld][lw3] 8267710: Hook AlwaysAtomicAccesses to primitive classes atomicity rules [v2]

[Aleksey Shipilev]

> `AlwaysAtomicAccesses` was added in JDK 9 to aid the research in the costs of requiring the always-atomic accesses. It would be nice to hook it up to current Valhalla code that handles explicitly declared atomic primitive classes.
> 
> Testing:
>  - [x] ad-hoc jcstress tests with lworld and `-XX:(-|+)AlwaysAtomicAccesses`

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Also add in another method

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Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/427/files
  - new: https://git.openjdk.java.net/valhalla/pull/427/files/8c18235d..b16de71e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=427&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=427&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/427.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/427/head:pull/427

PR: https://git.openjdk.java.net/valhalla/pull/427