RFR: JDK-8283143: Use minimal-length literals to initialize PI and E constants

[Joe Darcy]

Depending on the range of the number line, a double value has between 15 and 17 digits of decimal precision. The literals used to initialize Math.PI and Math.E have several digits more precision than that maximum.

That is potentially confusing to readers of the code and the minimum length strings to exactly represent the value in question should be used instead.

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Commit messages:
 - JDK-8283143: Use minimal-length literals to initialize PI and E constants

Changes: https://git.openjdk.java.net/jdk/pull/7814/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7814&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283143
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7814.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7814/head:pull/7814

PR: https://git.openjdk.java.net/jdk/pull/7814