RFR: JDK-8289551: Conversions between bit representations of half precision values and floats [v4]

[Joe Darcy]

> Initial implementation.

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

  Add NaN test.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9422/files
  - new: https://git.openjdk.org/jdk/pull/9422/files/420a9f3f..a30daf2f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9422&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9422&range=02-03

  Stats: 83 lines in 1 file changed: 83 ins; 0 del; 0 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