RFR: JDK-8294539: Augment discussion of equivalence relations on floating-point values [v2]

[Joe Darcy]

> While the floating-point == operation is *not* an equivalence relation, there are useful equivalence relations that can be defined over floating-point values. Text is added to java.lang.Double to discuss and name those relations.

Joe Darcy has updated the pull request incrementally with two additional commits since the last revision:

 - Add discussion of numerical equality.
 - Fix typo.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10498/files
  - new: https://git.openjdk.org/jdk/pull/10498/files/7d18585f..58543643

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10498&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10498&range=00-01

  Stats: 15 lines in 1 file changed: 12 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/10498.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10498/head:pull/10498

PR: https://git.openjdk.org/jdk/pull/10498