RFR: 8271602: Add Math.ceilDiv() family parallel to Math.floorDiv() family

[Raffaello Giulietti]

Please review this PR to add officially endorsed `ceilDiv()` and `ceilMod()` methods do `j.l.[Strict]Math`.

Beside adding fresh tests to `test/jdk/java/lang/Math/DivModTests.java`, this PR also corrects small typos in it and exercises tests that were already present but which were never invoked.
Let me know if this is acceptable for a test or if there's a need of a separate issue in the JBS.

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Commit messages:
 - 8271602: Add Math.ceilDiv() family parallel to Math.floorDiv() family

Changes: https://git.openjdk.java.net/jdk/pull/5285/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5285&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271602
  Stats: 871 lines in 3 files changed: 850 ins; 0 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5285.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5285/head:pull/5285

PR: https://git.openjdk.java.net/jdk/pull/5285