RFR: JDK-8302040: Port fdlibm sqrt to Java [v5]

[Joe Darcy]

> The wheel of FDLIBM porting turns a notch and sqrt comes into play.
> 
> While the sqrt operation usually has a hardware implementation that is intrinsified, for completeness a software implementation should be available as well.

Joe Darcy has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Enable intrinsic for StrictMath.sqrt; thanks to Tobias Hartmann for assistance with the HotSpot updates.
 - Merge branch 'master' into JDK-8302040
 - Implement review feedback.
 - Add one one unsigned shift comment.
 - Respond to review feedback.
 - JDK-8302040: Port fdlibm sqrt to Java

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12736/files
  - new: https://git.openjdk.org/jdk/pull/12736/files/ed06ecbb..f7a40d53

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12736&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12736&range=03-04

  Stats: 2865 lines in 76 files changed: 1654 ins; 745 del; 466 mod
  Patch: https://git.openjdk.org/jdk/pull/12736.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12736/head:pull/12736

PR: https://git.openjdk.org/jdk/pull/12736