RFR: JDK-8285869: Selective cleanup in doclint Checker class [v3]

[Jonathan Gibbons]

> Please review some localized cleanup for the doclint Checker class, primarily focused on upgrading to the use of "enhanced `switch`"
> 
> The output of one test was changed because of some improvements in one switch statement to eliminate the use of fall-through semantics.

Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  address review feedback

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8460/files
  - new: https://git.openjdk.java.net/jdk/pull/8460/files/edbb9247..7be7ab30

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8460&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8460&range=01-02

  Stats: 9 lines in 1 file changed: 0 ins; 6 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8460.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8460/head:pull/8460

PR: https://git.openjdk.java.net/jdk/pull/8460