<i18n dev> RFR: 8342682: Errors related to unused code on Windows after 8339120

[Julian Waters]

After 8339120, gcc began catching many different instances of unused code in the Windows specific codebase. Some of these seem to be bugs. I've taken the effort to mark out all the relevant globals and locals that trigger the unused warnings and addressed all of them by commenting out the code as appropriate. I am confident that in many cases this simplistic approach of commenting out code does not fix the underlying issue, and the warning actually found a bug that should be fixed. In these instances, I will be aiming to fix these bugs with help from reviewers, so I recommend anyone reviewing who knows more about the code than I do to see whether there is indeed a bug that needs fixing in a different way than what I did. This will require reviews from core-libs, awt, security, accessibility, jpackage, and whatever team is responsible for HotSpot debugging.

This fix requires C++17, so it will have to wait for the switch to C++17. I will be working towards that in the meantime and addressing the issues that come with changing the language standard elsewhere. This will only go in once the JDK actually starts using C++17

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Commit messages:
 - Compile as C++17
 - 8342682

Changes: https://git.openjdk.org/jdk/pull/21616/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21616&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342682
  Stats: 72 lines in 25 files changed: 25 ins; 1 del; 46 mod
  Patch: https://git.openjdk.org/jdk/pull/21616.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21616/head:pull/21616

PR: https://git.openjdk.org/jdk/pull/21616