RFR: 8294376: Minimize disabled warnings in java.base

[Magnus Ihse Bursie]

After [JDK-8294281](https://bugs.openjdk.org/browse/JDK-8294281), it is now possible to disable warnings for individual files instead for whole libraries. I used this opportunity to go through all disabled warnings in java.base native libraries.

Any warnings that were only triggered in a few files were removed from the library as a whole, and changed to be only disabled for those files.

Some warnings didn't trigger in any file anymore, and could just be removed.

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Commit messages:
 - Fixes for linux
 - Fix windows
 - Fix macos/aarch64

Changes: https://git.openjdk.org/jdk/pull/10426/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10426&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294376
  Stats: 26 lines in 2 files changed: 9 ins; 4 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/10426.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10426/head:pull/10426

PR: https://git.openjdk.org/jdk/pull/10426