RFR: JDK-8289551: Conversions between bit representations of half precision values and floats [v2]

[Joe Darcy]

> Initial implementation.

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 15 additional commits since the last revision:

 - Respond to review feedback.
 - Correct carry-out bug; add full binade test.
 - Improve NaN significand fidelity; refine tests.
 - Partial implementation of review feedback; test refinement.
 - Merge branch 'master' into JDK-8289551
 - Further refine spec.
 - Refine spec and tests.
 - Fix implementation thresholds; refine tests.
 - Initial implementation of float -> binary16 round-to-nearest with tests.
 - Implement review feedback from John Rose.
 - ... and 5 more: https://git.openjdk.org/jdk/compare/28899bfd...b09fdfc3

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9422/files
  - new: https://git.openjdk.org/jdk/pull/9422/files/399248d2..b09fdfc3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9422&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9422&range=00-01

  Stats: 3640 lines in 185 files changed: 1849 ins; 823 del; 968 mod
  Patch: https://git.openjdk.org/jdk/pull/9422.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9422/head:pull/9422

PR: https://git.openjdk.org/jdk/pull/9422