RFR: JDK-8189591: No way to locally suppress doclint warnings

[Jonathan Gibbons]

Please review a moderately simple change, to have DocLint check for relevant `@SuppressWarnings` annotations before reporting any messages.

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Commit messages:
 - JDK-8189591: No way to locally suppress doclint warnings

Changes: https://git.openjdk.java.net/jdk/pull/5870/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5870&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8189591
  Stats: 256 lines in 4 files changed: 246 ins; 5 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5870.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5870/head:pull/5870

PR: https://git.openjdk.java.net/jdk/pull/5870