RFR: JDK-8303794: IEEEremainder problems are causing test failures after JDK-8302801

[Joe Darcy]

Quick port of IEEEremainder; sorry for missing this earlier. Will add targeted tests in a follow-up fix.

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Commit messages:
 - Fixes.
 - JDK-8303794: IEEEremainder problems are causing test failures after JDK-8302801

Changes: https://git.openjdk.org/jdk/pull/12915/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12915&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303794
  Stats: 165 lines in 2 files changed: 164 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12915.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12915/head:pull/12915

PR: https://git.openjdk.org/jdk/pull/12915