RFR: 8274415: Suppress warnings on non-serializable non-transient instance fields in java.xml

[Joe Darcy]

Augmentations to javac's Xlint:serial checking are out for review (#5709) and the java.xml module would need some changes to pass under the expanded checks.

The changes are to suppress warnings where non-transient fields in serializable types are not declared with a type statically known to be serializable. That isn't necessarily a correctness issues, but it does merit further scrutiny.

I'll run a script to update the copyright years before pushing.

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Commit messages:
 - 8274415: Suppress warnings on non-serializable non-transient instance fields in java.xml

Changes: https://git.openjdk.java.net/jdk/pull/5730/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5730&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274415
  Stats: 45 lines in 27 files changed: 45 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5730.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5730/head:pull/5730

PR: https://git.openjdk.java.net/jdk/pull/5730