RFR: 8328630: Add logging when needed symbols in dll are missing.

[Robbin Ehn]

Hi, please consider this additional logging.

Thanks, Robbin

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Commit messages:
 - additional fixes
 - fixed NULL -> nullptr
 - add logging

Changes: https://git.openjdk.org/jdk/pull/18404/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18404&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328630
  Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18404.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18404/head:pull/18404

PR: https://git.openjdk.org/jdk/pull/18404