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

[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!

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Commit messages:
 - 8278757: [s390] Implement AES Counter Mode Intrinsic

Changes: https://git.openjdk.java.net/jdk/pull/8142/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8142&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278757
  Stats: 689 lines in 5 files changed: 669 ins; 5 del; 15 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