[foreign-abi] RFR: 8241309: foreign-abi branch has javadoc errors

[Maurizio Cimadamore]

This is a simple patch which fixes a bunch of doc errors preventing javadoc from terminating correctly.

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Commit messages:
 - JDK-8241309: foreign-abi branch has javadoc errors

Changes: https://git.openjdk.java.net/panama-foreign/pull/58/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/58/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8241309
  Stats: 13 lines in 4 files changed: 3 ins; 1 del; 9 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/58.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/58/head:pull/58

PR: https://git.openjdk.java.net/panama-foreign/pull/58