RFR: JDK-8271159: [REDO] JDK-8249634 doclint should report implicit constructor as missing javadoc comments

[Jonathan Gibbons]

Please review a do-over of JDK-8249634, to report a missing doc comment when an implicit/default constructor is used.

The `src` code is the same as before.   The previous version had missing test files (now added), and had a test fail because an interaction with another changeset that was pushed while the previous version was in review. The solution for that is the use of `-Xdoclint:all,-missing` in `TestDocTreeDiags.java`.

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Commit messages:
 - JDK-8271159: [REDO] JDK-8249634 doclint should report implicit constructor as missing javadoc comments

Changes: https://git.openjdk.java.net/jdk/pull/5088/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5088&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271159
  Stats: 240 lines in 77 files changed: 125 ins; 4 del; 111 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5088.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5088/head:pull/5088

PR: https://git.openjdk.java.net/jdk/pull/5088