RFR: JDK-8309595 Allow javadoc to process unnamed classes

[Jim Laskey]

Unnamed classes are rejected by javadoc because they are synthetic.

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Commit messages:
 - Enable javadoc for unnamed classes

Changes: https://git.openjdk.org/jdk/pull/14356/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14356&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309595
  Stats: 90 lines in 3 files changed: 89 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14356.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14356/head:pull/14356

PR: https://git.openjdk.org/jdk/pull/14356