RFR: JDK-8305591: Cleanup use of `newline` flag in DocCommentParser [v2]

[Jonathan Gibbons]

> Please remove a simple cleanup fix, to remove unnecessary assignments to set the `newline` flag  to `true` in `DocCommentParser`. The flag is always set appropriately in `nextChar()`.
> 
> This removes a number of "fall-through" cases in switch statements. In reviewing the use of `@SuppressWarnings("fall through")` it was noted that there is a missing `break` in `case '@'` in `inlineWord()`. Fixing this breaks a test. This will be addressed separately. [JDK-8305620](https://bugs.openjdk.org/browse/JDK-8305620)

Jonathan Gibbons has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Remove redundant @SuppressWarnings
 - Merge remote-tracking branch 'upstream/master' into 8305591.dcp-newline
 - JDK-8305591: Cleanup use of `newline` flag in DocCommentParser

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13341/files
  - new: https://git.openjdk.org/jdk/pull/13341/files/dc4697da..77922555

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13341&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13341&range=00-01

  Stats: 2729 lines in 66 files changed: 2445 ins; 40 del; 244 mod
  Patch: https://git.openjdk.org/jdk/pull/13341.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13341/head:pull/13341

PR: https://git.openjdk.org/jdk/pull/13341