RFR: 8287139: aarch64 intrinsic for unsignedMultiplyHigh

[Raffaello Giulietti]

Adds aarch64 intrinsic support for `Math.unsignedMultiplyHigh()`

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Commit messages:
 - 8287139: aarch64 intrinsic for unsignedMultiplyHigh

Changes: https://git.openjdk.java.net/jdk/pull/8840/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8840&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287139
  Stats: 16 lines in 1 file changed: 16 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8840.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8840/head:pull/8840

PR: https://git.openjdk.java.net/jdk/pull/8840