[jdk11u] RFR: 8251329: (zipfs) Files.walkFileTree walks infinitely if zip has dir named "." inside

[Martin Doerr]

Backport of 8251329: (zipfs) Files.walkFileTree walks infinitely if zip has dir named "." inside
The actual fix applies cleanly, but the comment changes in module-info.java need manual integration.
The new test requires adaption for 11u (see 2nd commit).

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Commit messages:
 - Adapt new test to JDK11.
 - Backport 3e3051e2ee93142983e9a3edee038e4f7b5ac0f2

Changes: https://git.openjdk.java.net/jdk11u/pull/19/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u&pr=19&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8251329
  Stats: 203 lines in 3 files changed: 202 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk11u/pull/19.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u pull/19/head:pull/19

PR: https://git.openjdk.java.net/jdk11u/pull/19