RFR: 8230623: Extract command-line help for -Xlint sub-options to new --help-lint [v4]

[Guoxiong Li]

> Hi all,
> 
> This patch splits out the concrete keys of -Xlint into a new option, --help-lint, 
> so that the output of --help-extra is kept clean and concise.
> 
> Thank you for taking the time to review.
> 
> Best Regards.

Guoxiong Li has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - Merge branch 'master' into JDK-8230623
 - Update copyright
 - Merge branch 'master' into JDK-8230623
 - Remove the content in documentation javac.1
 - 8230623: Extract command-line help for -Xlint sub-options to new --help-lint

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Changes: https://git.openjdk.java.net/jdk/pull/1758/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1758&range=03
  Stats: 62 lines in 4 files changed: 32 ins; 22 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1758.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1758/head:pull/1758

PR: https://git.openjdk.java.net/jdk/pull/1758