RFR: 8278757: [s390] Implement AES Counter Mode Intrinsic [v6]

[Lutz Schmidt]

> Please review (and approve, if possible) this pull request.
> 
> This is a s390-only enhancement. It introduces the implementation of an AES-CTR intrinsic, making use of the specific s390 instruction for AES counter-mode encryption.
> 
> Testing: SAP does no longer maintain a full build and test environment for s390. Testing is therefore limited to running some test suites (SPECjbb*, SPECjvm*) manually. But: identical code is contained in SAP's commercial product and thoroughly tested in that context. No issues were uncovered.
> 
> @backwaterred Could you please conduct some "official" testing for this PR? 
> 
> Thank you all!
> 
> Note: some performance figures can be found in the JBS ticket.

Lutz Schmidt has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch 'JDK-8278757' of ssh://github.com/RealLucy/jdk into JDK-8278757
   Merge to bring local branch up-to-date
 - 8278757: honor review comments part 1

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8142/files
  - new: https://git.openjdk.java.net/jdk/pull/8142/files/7b40f945..a99a6fbe

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8142&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8142&range=04-05

  Stats: 46 lines in 1 file changed: 7 ins; 25 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8142.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8142/head:pull/8142

PR: https://git.openjdk.java.net/jdk/pull/8142