[jdk11u-dev] RFR: 8263432: javac may report an invalid package/class clash on case insensitive filesystems

[Martin Doerr]

Backport of JDK-8263432. Fix applies cleanly except Copyright year update. The test required manual integration and adaptation of imports.

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Commit messages:
 - Backport 0a4c33826d0422af7c4cfa5f479fe0b6b0f83d23

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/184/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=184&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263432
  Stats: 107 lines in 2 files changed: 102 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/184.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/184/head:pull/184

PR: https://git.openjdk.java.net/jdk11u-dev/pull/184