RFR: 8261862: Expand discussion of rationale for BigDecimal equals/compareTo semantics [v2]

[Joe Darcy]

> I considered @stuart-marks previous suggestion during the code review of JDK-8261123 to include a more explicit discussion of why, say, different representations of 2 should not be regarded as equivalent. After contemplating several alternatives, I didn't find anything simpler than Stuart's 2/3 example so I used that as seen in the diff.
> 
> A short digression, BigDecimal supports both fixed-point style and floating-point style rounding. Floating-point rounding primarily replies on the number of precision digits, regards of their scale, while fixed-point style rounding prioritizes the scale. The number of digits of eventual output is a function of number number of digits in the inputs and the number of precision digits in a floating-point style rounding. A floating-point style rounding has a preferred scale, rather than a fixed scale based on the inputs. The fixed-point style divide method used in the example has a scale based on the dividend, allowing a relatively simple expression to show a distinction between 2.0 and 2.00.

Joe Darcy has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Respond to review feedback and reflow paragraphs.
 - Merge branch 'master' into 8261862
 - 8261862: Expand discussion of rationale for BigDecimal equals/compareTo semantics

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2804/files
  - new: https://git.openjdk.java.net/jdk/pull/2804/files/48b49386..75b27c3f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2804&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2804&range=00-01

  Stats: 774 lines in 17 files changed: 703 ins; 13 del; 58 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2804.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2804/head:pull/2804

PR: https://git.openjdk.java.net/jdk/pull/2804