RFR: JDK-8290901: Reduce use of -source in langtools tests [v3]

[Joe Darcy]

> To a first approximation, this change replaces use of "-source", where possible, with the preferable "--release" javac option. (There are cases where this swap is not desirable, such as when newer library features are being used in the test.)
> 
> A few unneeded uses of -source were removed entirely.
> 
> I'll update copyrights before any push.

Joe Darcy 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 four additional commits since the last revision:

 - Remove unneeded -Xlint:-options flag
 - Merge branch 'master' into JDK-8290901
 - Update copyrights.
 - JDK-8290901: Reduce use of -source in langtools tests

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9622/files
  - new: https://git.openjdk.org/jdk/pull/9622/files/a375ff8b..3a6cb666

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9622&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9622&range=01-02

  Stats: 5738 lines in 278 files changed: 3270 ins; 1884 del; 584 mod
  Patch: https://git.openjdk.org/jdk/pull/9622.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9622/head:pull/9622

PR: https://git.openjdk.org/jdk/pull/9622