[lworld+fp16] RFR: 8334432: Refine Float16.fma [v4]

[Joe Darcy]

> Adding comments and test cases for Float16.fma.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Add testing of neighbors of half-way cases for double -> Float16 conversion.

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1143/files
  - new: https://git.openjdk.org/valhalla/pull/1143/files/ea5f4bf0..46a84462

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1143&range=03
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1143&range=02-03

  Stats: 13 lines in 1 file changed: 9 ins; 0 del; 4 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