[lworld+fp16] RFR: 8339098: Add class jdk.internal.math.Float16Consts

[Raffaello Giulietti]

Adding class Float16Consts to parallel DoubleConsts and FloatConsts.

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Commit messages:
 - 8339098: Add class jdk.internal.math.Float16Consts

Changes: https://git.openjdk.org/valhalla/pull/1226/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1226&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339098
  Stats: 93 lines in 1 file changed: 93 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1226.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1226/head:pull/1226

PR: https://git.openjdk.org/valhalla/pull/1226