[lworld+fp16] RFR: 8334432: Refine Float16.fma [v8]

[Joe Darcy]

> Adding comments and test cases for Float16.fma.

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 10 additional commits since the last revision:

 - Respond to review feedback.
 - Merge branch 'lworld+fp16' into JDK-8334432
 - Respond to review feedback.
 - Fix typo in test comments.
 - Add tests for subnromal results.
 - Add testing of neighbors of half-way cases for double -> Float16 conversion.
 - Added testing for valueOf(double).
 - Respond to review feedback.
 - Merge branch 'lworld+fp16' into JDK-8334432
 - JDK-8334432: Refine Float16.fma

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1143/files
  - new: https://git.openjdk.org/valhalla/pull/1143/files/172eea95..2d357510

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1143&range=07
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1143&range=06-07

  Stats: 1431 lines in 35 files changed: 1141 ins; 175 del; 115 mod
  Patch: https://git.openjdk.org/valhalla/pull/1143.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1143/head:pull/1143

PR: https://git.openjdk.org/valhalla/pull/1143