RFR: 8188044: We need Math.unsignedMultiplyHigh [v4]

[Brian Burkhalter]

> Please consider this proposal to add a method `unsignedMultiplyHigh(long,long)` to each of `java.lang.Math` and `java.lang.StrictMath`.

Brian Burkhalter has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8188044: Use multiplyHigh() to leverage the intrinsic

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4644/files
  - new: https://git.openjdk.java.net/jdk/pull/4644/files/2ad5e395..a499b2e5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4644&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4644&range=02-03

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4644.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4644/head:pull/4644

PR: https://git.openjdk.java.net/jdk/pull/4644