RFR: JDK-8275360: Use @Override in javax.annotation.processing

[Joe Darcy]

Simple cleanup to add @Override annotations to AbstractProcessor. IIRC when AbstractProcessor was added in JDK 6, using @Override wasn't yet support for interface methods.

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Commit messages:
 - JDK-8275360: Use @Override in javax.annotation.processing

Changes: https://git.openjdk.java.net/jdk/pull/5979/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5979&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275360
  Stats: 6 lines in 2 files changed: 5 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5979.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5979/head:pull/5979

PR: https://git.openjdk.java.net/jdk/pull/5979