RFR: 4511638: Double.toString(double) sometimes produces incorrect results

[Raffaello Giulietti]

Hello,

here's a PR for a patch submitted on March 2020 [1](https://cr.openjdk.java.net/~bpb/4511638/webrev.04/) when Mercurial was a thing.

The patch has been edited to adhere to OpenJDK code conventions about multi-line (block) comments. Nothing in the code proper has changed, except for the addition of redundant but clarifying parentheses in some expressions.


Greetings
Raffaello

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Commit messages:
 - 4511638: Double.toString(double) sometimes produces incorrect results

Changes: https://git.openjdk.java.net/jdk/pull/3402/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3402&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-4511638
  Stats: 4237 lines in 15 files changed: 4116 ins; 54 del; 67 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3402.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3402/head:pull/3402

PR: https://git.openjdk.java.net/jdk/pull/3402