RFR: JDK-8259530: Generated docs contain MIT/GPL-licenced works without reproducing the licence

[Jonathan Gibbons]

Please review a change for JavaDoc, for the Standard Doclet to copy legal header files into the generated docs from a default or designated directory.

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Commit messages:
 - JDK-8259530: Generated docs contain MIT/GPL-licenced works without reproducing the licence

Changes: https://git.openjdk.java.net/jdk/pull/3954/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3954&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259530
  Stats: 253 lines in 7 files changed: 249 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3954.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3954/head:pull/3954

PR: https://git.openjdk.java.net/jdk/pull/3954