[jdk11u-dev] RFR: 8213263: fix legal headers in test/langtools

[Christoph Langer]

Backport of JDK-8213263.

Applies cleanly but following files don't exist in 11u:

test/langtools/jdk/javadoc/doclet/testHeadTag/TestHeadTag.java
test/langtools/jdk/javadoc/doclet/testHtmlLandmarkRegions/TestHtmlLankmarkRegions.java
test/langtools/jdk/javadoc/doclet/testIndexTaglet/TestIndexTaglet.java
test/langtools/tools/javac/switchexpr/ExpressionSwitchInExpressionSwitch.java

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Commit messages:
 - Backport 73fa99ae866defd67cae7604fca012825c82283e

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/322/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=322&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8213263
  Stats: 520 lines in 159 files changed: 0 ins; 360 del; 160 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/322.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/322/head:pull/322

PR: https://git.openjdk.java.net/jdk11u-dev/pull/322