RFR: 6996: Properly support converters [v4]

[Marcus Hirt]

> Including simple test to verify that the resulting instrumented methods are ok.

Marcus Hirt has updated the pull request incrementally with two additional commits since the last revision:

 - Formatting
 - Fixes, cleanup and more tests

-------------

Changes:
  - all: https://git.openjdk.java.net/jmc/pull/168/files
  - new: https://git.openjdk.java.net/jmc/pull/168/files/301cd691..4ea8707e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=168&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=168&range=02-03

  Stats: 695 lines in 24 files changed: 636 ins; 3 del; 56 mod
  Patch: https://git.openjdk.java.net/jmc/pull/168.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/168/head:pull/168

PR: https://git.openjdk.java.net/jmc/pull/168