RFR: 6785: Compiler warning cleanup

[Marcus Hirt]

Cleaning up various compiler warnings. I've opened issues for some internal deprecated JMC APIs that we will need to
discuss a bit further.

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Commit messages:
 - Formatting fix
 - Formatting fix
 - More cleanup
 - More cleanup
 - More cleanup
 - More cleanup
 - More cleanup
 - More cleanup
 - More cleanup
 - Deprecated use
 - ... and 7 more: https://git.openjdk.java.net/jmc/compare/5825cb40...4cb345e5

Changes: https://git.openjdk.java.net/jmc/pull/75/files
 Webrev: https://webrevs.openjdk.java.net/jmc/75/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6785
  Stats: 175 lines in 53 files changed: 55 ins; 80 del; 40 mod
  Patch: https://git.openjdk.java.net/jmc/pull/75.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/75/head:pull/75

PR: https://git.openjdk.java.net/jmc/pull/75