RFR: 7509: Add 2021-09 target platform [v3]

[Marcus Hirt]

> ...also updating babel.

Marcus Hirt has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:

 - Merge branch 'master' into 7509-2021-09
 - Fixed version
 - 7509: Add 2021-09 target platform
 - Fixing copyright years
 - Further project files and fixes
 - 7505: Fixing project setup

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Changes: https://git.openjdk.java.net/jmc/pull/357/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=357&range=02
  Stats: 115 lines in 6 files changed: 107 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jmc/pull/357.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/357/head:pull/357

PR: https://git.openjdk.java.net/jmc/pull/357