RFR: 8205502: Make exception message from AnnotationInvocationHandler more informative

[Joe Darcy]

Simple change to make the exception/error messages more informative for various malformed annotation situations.

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Commit messages:
 - Appease jcheck.
 - 8205502: Make exception message from AnnotationInvocationHandler more informative

Changes: https://git.openjdk.java.net/jdk/pull/3317/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3317&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8205502
  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3317.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3317/head:pull/3317

PR: https://git.openjdk.java.net/jdk/pull/3317