RFR: 8273346: Expand library mappings to IEEE 754 operations

[Joe Darcy]

Generally add apiNote's to map from Java library methods to particular IEEE 754 operations. For now, I only added such notes to java.lang.Math and not java.lang.StrictMath.

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Commit messages:
 - Add floor and ceil.
 - JDK-8273346: Examine use of "rounding mode" and "rounding policy" in Math and StrictMath

Changes: https://git.openjdk.java.net/jdk/pull/8876/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8876&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273346
  Stats: 108 lines in 4 files changed: 103 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8876.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8876/head:pull/8876

PR: https://git.openjdk.java.net/jdk/pull/8876