RFR: Improve combining of nested review replies

[Robin Westberg]

Hi all,

Please review this change that improves combining review comment replies. As GitHub allows replying in batches to multiple review comments, such replies should be combined into a single email when possible.

Best regards,
Robin

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Commits:
 - 0859c0bc: Improve combining of nested review replies

Changes: https://git.openjdk.java.net/skara/pull/475/files
 Webrev: https://webrevs.openjdk.java.net/skara/475/webrev.00
  Stats: 51 lines in 2 files changed: 33 ins; 4 del; 14 mod
  Patch: https://git.openjdk.java.net/skara/pull/475.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/475/head:pull/475

PR: https://git.openjdk.java.net/skara/pull/475